Laser irradiation apparatus

ABSTRACT

Each region, which should be left on a substrate after patterning, of a semiconductor film is grasped in accordance with a mask. Then, each region to be scanned with laser light is determined so that at least the region to be obtained through the patterning is crystallized, and a beam spot is made to hit the region to be scanned, thereby partially crystallizing the semiconductor film. Each portion with low output energy of the beam spot is shielded by a slit. In the present invention, the laser light is not scanned and irradiated onto the entire surface of the semiconductor film but is scanned such that at least each indispensable portion is crystallized to a minimum. With the construction described above, it becomes possible to save time taken to irradiate the laser light onto each portion to be removed through the patterning after the crystallization of the semiconductor film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a laser irradiation equipment thatcrystallize a semiconductor film using laser light and activate after anion implantation.

2. Description of the Related Art

In recent years, a technique of forming a TFT on a substrate has greatlyprogressed, and its application and development for active matrixsemiconductor display device has been advanced. In particular, since aTFT using a polycrystalline semiconductor film has higher field-effectmobility than a TFT using a conventional amorphous silicon film, itenables high speed operation. Therefore, although the pixel isconventionally controlled on a driving circuit provided outside thesubstrate, it is possible to control the pixel on the driving circuitformed on the same substrate.

Incidentally, as the substrate used in the semiconductor device, a glasssubstrate is expected hopefully as the substrate in comparison with asingle crystal silicon substrate in terms of the cost. Since a glasssubstrate is inferior in heat resistance and is susceptible toheat-deformation, in the case where a polysilicon TFT is formed on theglass substrate, laser annealing is used for crystallization of thesemiconductor film in order to avoid heat-deformation of the glasssubstrate.

Characteristics of laser annealing are as follows: it can greatly reducea processing time in comparison with an annealing method using radiationheating or conductive heating; and it hardly causes thermal damage tothe substrate by selectively and locally heating a semiconductor or thesemiconductor film.

Note that the laser annealing method here indicates a technique ofrecrystallizing the damaged layer formed on the semiconductor substrateor the semiconductor film, and a technique of crystallizing theamorphous semiconductor film formed on the substrate. Also, the laserannealing method here includes a technique applied to leveling orsurface reforming of the semiconductor substrate or the semiconductorfilm. A laser oscillation apparatus applied is a gas laser oscillationapparatus represented by an excimer laser or a solid laser oscillationapparatus represented by a YAG laser. It is known as the apparatus whichperforms crystallization by heating a surface layer of the semiconductorby irradiation of the laser beam in an extremely short period of time ofabout several ten nanoseconds to several hundred microseconds.

Lasers are roughly divided into two types: pulse oscillation andcontinuous oscillation, according to an oscillation method. In the pulseoscillation laser, an output energy is relatively high, so that massproductivity can be increased assuming the size of a beam spot to beseveral cm² or more. In particular, when the shape of the beam spot isprocessed using an optical system and made to be a linear shape of 10 cmor more in length, it is possible to efficiently perform irradiation ofthe laser beam to the substrate and further enhance the massproductivity. Therefore, for crystallization of the semiconductor film,the use of a pulse oscillation laser is becoming mainstream.

However, in recent years, in crystallization of the semiconductor film,it is found that grain size of the crystal formed in the semiconductorfilm is larger in the case where the continuous oscillation laser isused than the case where the pulse oscillation laser is used. When thecrystal grain size in the semiconductor film becomes large, the mobilityof the TFT formed using the semiconductor film becomes high andvariation of the TFT characteristics due to a grain boundary issuppressed. Therefore, a continuous oscillation laser is recentlyattracting attention.

However, since the maximum output energy of the continuous oscillationlaser is generally small in comparison with that of the pulseoscillation laser, the size of the beam spot is small, which is about10⁻³ mm². Accordingly, in order to treat one large substrate, it isnecessary to move a beam irradiation position on the substrate upwardand downward, and right and left, it results in increasing theprocessing time per one substrate. Thus, processing efficiency is poorand it is an important object to improve the processing speed of thesubstrate.

A technique for high processing efficiency of substrate by overlappingand condensing a plurality of beam spots to form one beam spot is wellknown (For example, Patent Literatures 1 and 2).

-   Patent Literature 1: Japanese Publication of Laid-Open Patent    Application No. Hei. 5-315278 (FIG. 11)-   Patent Literature 2: Japanese Publication of Laid-Open Patent    Application No. Hei. 4-282869 (second to third pages, FIG. 1A)

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problems, andtherefore it is an object of the present invention to provide a laserirradiation equipment using the laser crystallizing method, which canenhance a processing efficiency of a substrate and the mobility of asemiconductor film in comparison with the conventional example.

The laser irradiation apparatus of the present invention includes: aplurality of first means (laser oscillation apparatuses) for oscillatinglaser lights; a second means (optical system) for condensing the laserlights oscillated from the plurality of laser oscillation apparatusesand having beam spots on an object to be processed partially overlapeach other, thereby synthesizing the beam spots; a slit that is capableof shielding a part of a beam spot obtained as a result of thesynthesizing; a third means for controlling a position of the beam spotirradiated through the slit on the object to be processed; and a fourthmeans for controlling oscillation by each of the plurality of firstmeans and synchronizing the plurality of laser oscillation apparatusesand the third means so that the beam spot irradiated through the slitcovers each region that has been determined in accordance with data(pattern information) concerning the shape of a mask and should becrystallized.

It should be noted here that it does not matter whether the region thathas been determined in accordance with the pattern information andshould be crystallized is a region of a semiconductor film that will beobtained through patterning after the crystallization or a regionthereof that will become the channel formation region of a TFT. In thepresent invention, the fourth means grasps the region that should becrystallized, determines the scanning path of the laser lights so thatthe laser lights are scanned onto at least the region that should becrystallized, and controls the third means so that the beam spot movesin accordance with the scanning path. That is, in the present invention,the laser lights are not irradiated onto the entire surface of thesemiconductor film but are scanned so that at least each indispensableportion is crystallized to a minimum. With the construction describedabove, it becomes possible to save a time taken to irradiate the laserlights onto each portion to be removed through patterning after thecrystallization of the semiconductor film.

As described above, in the present invention, the laser lights are notscanned and irradiated onto the entire surface of the semiconductor filmbut are scanned so that at least each indispensable portion iscrystallized, which makes it possible to save a time taken to irradiatethe laser lights onto each portion to be removed through the patterningafter the crystallization of the semiconductor film. As a result, itbecomes possible to shorten a time taken to irradiate the laser lightsand also to improve the speed at which a substrate is processed.

Also, by synthesizing the laser lights oscillated from the plurality oflaser oscillation apparatuses, it becomes possible to have the laserlights complement each other in each portion having a low energydensity. Further, by performing the laser light irradiation through theslit, it becomes possible to shield each portion, which has a low energydensity, of the beam spot obtained as a result of the synthesizing. As aresult, it becomes possible to irradiate laser light, whose energydensity is relatively uniform, onto the semiconductor film and touniformly perform the crystallization. Also, by providing the slit, itbecomes possible to partially change the width of the beam spot inaccordance with the pattern information and to reduce limitationsimposed on the layout of active layers of TFTs. Note that, the width ofa beam spot refers to the length of the beam spot in a directionvertical to a scanning direction.

Further, in the present invention, in order to irradiate the laserlights in accordance with the pattern information concerning the mask,after the formation of the semiconductor film, markers are given to thesemiconductor film with a laser light prior to the crystallization withthe laser lights. Following this, with reference to positions of themarkers, each position, at which the laser lights should be scanned, isdetermined based on the mask.

It should be noted here that the irradiation of the laser lights may beperformed twice or more. In the case where the irradiation of the laserlights is performed twice, the scanning path of the laser lights duringthe first irradiation operation is determined so that the laser lightsare irradiated onto the region that has been determined in accordancewith the pattern information and should be crystallized, and the thirdmeans is controlled so that the beam spot moves in accordance with thescanning path. Next, the scanning direction is changed by controllingthe third means, the scanning path of the laser lights during the secondirradiation operation is determined so that the laser lights areirradiated onto the region that has been determined in accordance withthe pattern information and should be crystallized, and the third meansis controlled so that the beam spot moves in accordance with thescanning path. At this time, it is preferable that the scanningdirection during the first laser light irradiation operation and thescanning direction during the second laser light irradiation operationform an angle that is closer to 90°.

With the construction described above, some crystal grains obtained bythe first laser light irradiation operation are converted into a singlelarger crystal grain by the second laser light irradiation operationwhose scanning direction has been changed. This may be because thecrystal grains that have grown in a specific direction during the firstlaser light irradiation operation function as seed crystals and crystalgrowing is performed during the second laser light irradiation operationin a direction that differs from the specific direction. As a result, asemiconductor film that has high crystallinity in part is obtainedthrough the laser light irradiation performed twice while changing thescanning direction. Therefore, by producing the active layers of TFTsusing the regions, whose crystallinity has been further enhanced, of thesemiconductor film, it becomes possible to obtain TFTs having highmobility.

Also, after the formation of the semiconductor film, the irradiation ofthe laser lights for crystallizing the semiconductor film may beperformed under a state where the exposure to the atmosphere isprevented (for instance, the laser light irradiation is performed undera specific gas atmosphere (such as a rare gas atmosphere, a nitrogenatmosphere, or an oxygen atmosphere) or under a reduced pressureatmosphere). With this construction, it becomes possible to prevent themixing of a contaminant (boron contained in a filter used to enhance thecleanness of the air, for instance) at a molecule level within a cleanroom into the semiconductor film during the crystallization using thelaser lights.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 shows a construction of a laser irradiation apparatus of thepresent invention;

FIGS. 2A and 2B respectively show a shape of a laser beam and adistribution of an energy density thereof;

FIGS. 3A and 3B respectively show a shape of a laser beam and adistribution of an energy density thereof;

FIGS. 4A to 4C each show a positional relation between a beam spot and aslit;

FIGS. 5A and 5B each show a positional relation between a portion to beirradiated with laser lights and masks;

FIGS. 6A and 6B each show a positional relation between a beam spot anda slit;

FIGS. 7A and 7B show a direction in which laser lights move on an objectto be processed;

FIGS. 8A to 8C show directions in which laser lights move on an objectto be processed;

FIGS. 9A and 9B each show a positional relation between portions to beirradiated with laser lights and masks;

FIGS. 10A and 10B each show a direction in which laser lights move on anactive layer of a TFT;

FIGS. 11A and 11B each show a positional relation between portions to beirradiated with laser lights and masks;

FIGS. 12A and 12B each show a positional relation between portions to beirradiated with laser lights and masks;

FIGS. 13A and 13B each show directions in which laser lights move on anactive layer of a TFT;

FIG. 14 shows a positional relation between portions to be irradiatedwith laser lights and masks for respective circuits;

FIGS. 15A and 15B each show positions of markers;

FIG. 16 shows a production flow of the present invention;

FIG. 17 shows a production flow of the present invention;

FIG. 18 shows a conventional production flow;

FIGS. 19A to 19E illustrate a mechanism of crystallization using an SLSmethod;

FIGS. 20A to 20E illustrate a mechanism of crystallization using an SLSmethod;

FIGS. 21A and 21B show each an optical system of the laser irradiationapparatus;

FIG. 22 shows an optical system of the laser irradiation apparatus;

FIG. 23 shows an optical system of the laser irradiation apparatus;

FIG. 24 shows an optical system of the laser irradiation apparatus;

FIG. 25 shows an optical system of the laser irradiation apparatus;

FIGS. 26A and 26B each show a positional relation between portions to beirradiated with laser lights and masks;

FIGS. 27A and 27B each show a positional relation between portions to beirradiated with laser lights and masks;

FIGS. 28A and 28B each show a direction in which laser lights move on anobject to be processed;

FIGS. 29A and 29B each show a direction in which laser lights move on anobject to be processed;

FIG. 30 shows a direction in which laser lights move on an object to beprocessed;

FIGS. 31A and 31B show a construction of markers;

FIG. 32 shows the construction of an optical system for markers;

FIGS. 33A to 33C show a method of producing a semiconductor device usinga laser irradiation apparatus of the present invention;

FIGS. 34A to 34C also show the method of producing the semiconductordevice using the laser irradiation apparatus of the present invention;

FIGS. 35A to 35C also show the method of producing the semiconductordevice using the laser irradiation apparatus of the present invention;

FIG. 36 also shows the method of producing the semiconductor deviceusing the laser irradiation apparatus of the present invention;

FIG. 37 shows a liquid crystal display apparatus produced using a laserirradiation apparatus of the present invention;

FIGS. 38A and 38B shows a method of producing a light-emitting apparatususing a laser irradiation apparatus of the present invention;

FIG. 39 is a cross-sectional view of a light-emitting apparatus producedusing a laser irradiation apparatus of the present invention;

FIG. 40 shows a production flow of the present invention;

FIG. 41 shows a method of producing a light-emitting apparatus using alaser irradiation apparatus of the present invention;

FIG. 42 shows a production flow of the present invention;

FIGS. 43A and 43B each show a state where a driving circuit isimplemented on a panel;

FIGS. 44A to 44H each show electronic equipment that use a semiconductordevice of the present invention;

FIG. 45 shows a distribution of an energy density of beam spots made tooverlap each other in the center axis direction;

FIG. 46 shows a relation between the distance between centers of beamspots and an energy difference;

FIG. 47 shows the distribution of an output energy of a beam spot in thecenter axis direction;

FIG. 48 is a cross-sectional view of a light-emitting apparatus using alaser irradiation apparatus of the present invention; and

FIG. 49 is a cross-sectional view of a light-emitting apparatus producedusing a laser apparatus of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a construction of the laser irradiation apparatus of thepresent invention will be described with reference to FIG. 1. Referencenumeral 101 denotes laser oscillation apparatuses. Four laseroscillation apparatuses are used in FIG. 1, although the number of laseroscillation apparatuses possessed by the laser irradiation apparatus ofthe present invention is not limited to this.

It is possible to change the laser as appropriate depending on thepurpose of processing. In the present invention, it is possible to use apublicly known laser. As the laser, it is possible to use a gas laser orsolid-state laser of pulse oscillation or continuous oscillation. As thegas laser, it is possible to cite an excimer laser, an Ar laser, a Krlaser, and the like. As the solid-state laser, it is possible to cite aYAG laser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, a glass laser, aruby laser, an alexandrite laser, a Ti: sapphire laser, a Y₂O₃ laser,and the like. As the solid-state laser, there is applied a laser thatuses a crystal such as YAG, YVO₄, YLF, YAlO₃, or the like doped with Cr,Nd, Er, Ho, Ce, Co, Ti, Yb, or Tm. The fundamental wave of the laserdiffers depending on a material to be doped with and there is obtained alaser light having a fundamental wave in the neighborhood of 1 μm. It ispossible to obtain a harmonic wave with respect to the fundamental waveusing a nonlinear optical element.

Also, it is further possible to use an ultraviolet laser light obtainedby converting an infrared laser light emitted from a solid-state laserinto a green laser light using a nonlinear optical element and byfurther processing the green laser light using another nonlinear opticalelement.

It should be noted here that the laser oscillation apparatuses 101 maybe constructed so that their temperatures are maintained constant usinga chiller 102. It is not necessarily required to use the chiller 102,although by maintaining the temperatures of the laser oscillationapparatuses 101 constant, it becomes possible to suppress variations inenergy of laser lights to be outputted that varies depending on thetemperatures.

Also, reference numeral 104 denotes an optical system that is capable ofcondensing the laser lights by changing the optical paths of the lightsoutputted from the laser oscillation apparatuses 101 and processing theshapes of beam spots of the lights. Further, the important pointconcerning the optical system 104 of the present invention is that it ispossible to synthesize the beam spots of the laser lights outputted fromthe plurality of laser oscillation apparatuses 101 by having the beamspots partially overlap each other.

It should be noted here that AO modulators 103 that change the travelingdirections of the laser lights within an extremely short time period maybe provided on the optical path between a substrate 106 that is anobject to be processed and the laser oscillation apparatuses 101.

A beam spot obtained by synthesizing the beam spots is irradiated ontothe substrate 106 that is an object to be processed through a slit 105.It is preferable that this slit 105 is formed using a material that iscapable of blocking the laser lights and is not deformed or damaged bythe laser lights. In addition, the width of the slit 105 is changeable,which makes it possible to change the width of the beam spot on thesubstrate 106 in accordance with the width of the slit.

It should be noted here that in the case where the laser lightsoscillated from the laser oscillation apparatuses 101 do not passthrough the slit 105, the shape of the beam spot obtained from the laserlights on the substrate 106 varies depending on the kind of the laserand it is possible to shape the beam spot with an optical system.

The substrate 106 is placed on a stage 107. In FIG. 1, position controlmeans 108 and 109 correspond to means for controlling the position ofthe beam spot on the object to be processed, and the position of thestage 107 is controlled by these position control means 108 and 109.Note that it is possible to move (scan) the beam spot and to change thescanning direction of the laser lights by changing the position of thesubstrate using the position control means 108 and 109 in FIG. 1,although the present invention is not limited to this construction. Forinstance, the irradiation direction of the laser lights may be changedusing an optical system. In this case, it is possible to interpret thatthe position control means are included in this optical system. Also,the irradiation direction may be changed using both of the moving of thesubstrate and the optical system.

In FIG. 1, the position control means 108 controls the position of thestage 107 in an X direction, while the position control means 109controls the position of the stage 107 in a Y direction.

Also, the laser irradiation apparatus of the present invention includesa computer 110 that has both of a central processing unit and a storagemeans such as a memory. This computer 110 is capable of controlling theoscillation operation of the laser oscillation apparatuses 101,controlling the position control means 108 and 109 so that the beam spotof the laser lights cover an area determined in accordance with patterninformation concerning masks, and setting the substrate at apredetermined position.

In the present invention, the computer 110 is also capable ofcontrolling the width of the slit 105, thereby changing the width of thebeam spot in accordance with the pattern information concerning themasks.

The laser irradiation apparatus may further include a means foradjusting the temperature of the object to be processed. Also, the laserlights are light having directivity and a high energy density, so that adumper may be provided in order to prevent a situation where reflectionlight is irradiated onto an inappropriate area. It is preferable thatthe dumper has a property of absorbing the reflection light. Also, bycirculating a coolant in the dumper, there may be prevented a situationwhere the temperature of a partition wall rises due to the absorption ofthe reflection light. Also, the stage 107 may be provided with a means(substrate heating means) for heating the substrate.

It should be noted here that in the case where the markers are formedwith a laser, there may be provided a laser oscillation apparatus 111for forming the markers. In this case, the oscillation by the laseroscillation apparatus 111 may be controlled by the computer 110.Further, in the case where the laser oscillation apparatus 111 isprovided, there is provided an optical system 112 that condenses thelaser light outputted from the laser oscillation apparatus 111.

Also, in order to perform alignment using the markers, there may beprovided one CCD camera 113. Alternatively, a plurality of CCD camerasmay be provided according to circumstances.

Next, there will be described the shape of a beam spot formed bysynthesizing a plurality of beam spots through overlapping.

FIG. 2A shows an example of the shape of a beam spot of the laser lightoscillated from each of the plurality of laser oscillation apparatuseson the object to be processed in the case where the laser light does notpass through the slit. The beam spot shown in FIG. 2A has an ellipticshape. Note that in the laser irradiation apparatus of the presentinvention, the beam spots of the laser lights oscillated from the laseroscillation apparatuses are not limited to the elliptic shape. Theshapes of the beam spots vary depending on the kind of the laser and itis possible to shape the beam spots with an optical system. Forinstance, the laser light emitted from the XeCl excimer laser (whosewavelength is 308 nm and pulse width is 30 ns) L3308 manufactured byLambda K.K. has a rectangular shape whose size is 10 mm×30 mm (both ofwhich are the half width in a beam profile). Also, the laser lightemitted from the YAG laser has a circular shape if a rod has acylindrical shape, and has a rectangular shape if the rod has a slabshape. Also, by further shaping such a laser light with an opticalsystem, it is also possible to generate a laser light having a desiredsize.

FIG. 2B shows the distribution of the energy density of the laser lightin a major axis L direction of the beam spot shown in FIG. 2A. As to thedistribution of the energy density of the laser light whose beam spothas the elliptic shape, the energy density is increased in accordancewith the reduction of a distance to the center “O” of the ellipse. Therange specified by “α” corresponds to a width in the major axis ydirection where the energy density exceeds a value that is necessary toobtain a desired crystal.

Next, FIG. 3A shows the shape of a beam spot obtained by synthesizinglaser lights that each have the beam spot shown in FIGS. 2A and 2B. Notethat a case where one beam spot is formed by having beam spots of fourlaser lights overlap each other is shown in FIG. 3A, although the numberof beam spots that are made to overlap each other is not limited tothis.

As shown in FIG. 3A, the beam spots of respective laser lights aresynthesized by arranging the major axes of respective ellipses on thesame straight line and having the beam spots partially overlap eachother. In this manner, there is formed one beam spot. Note that astraight line obtained by connecting the centers “O” of respectiveellipses will be hereinafter referred to as the “center axis”.

FIG. 3B shows the distribution of energy densities of the laser lightsin a direction of the center axis of the beam spot shown in FIG. 3Aobtained as a result of the synthesizing. There is increased the energydensity in each portion in which respective beam spots before thesynthesizing overlap each other. For instance, if the energy densities Aand B of beams that overlap each other in the illustrated manner areadded to each other, the addition result becomes approximately equal tothe peak value C of the energy density of the beam and the energydensity is flattened in each portion between the centers “O” ofrespective ellipses.

It should be noted here that it is ideal that a result obtained byadding A to B becomes equal to C, although the actual addition resultdoes not necessarily become a value that is equal to C. It is sufficientthat the difference between the value obtained by adding A to B and thevalue of C is in a range of ±10% of the value of C, more preferably, ina range of ±5% thereof. However, it is possible for a designer to setthe permissible range as appropriate.

As can be seen from FIG. 3B, by having a plurality of laser lightsoverlap each other and having the laser lights complement each other ineach portion having a low energy density, it becomes possible to enhancethe crystallinity of a semiconductor film with efficiency in comparisonwith a case where the plurality of laser lights are not made to overlapeach other and are used independently of each other. For instance, it isassumed that in FIG. 2B, the energy density exceeds a value that isnecessary to obtain the desired crystal only in the area specified bythe sloped lines and the energy densities in other areas are below thedesired value. In this case, the desired crystal is obtained with eachbeam spot only in the sloped-line area whose width in the center axisdirection is indicated by “α”. However, as shown in FIG. 3B, by havingthe beam spots overlap each other, it becomes possible to obtain thedesired crystal in an area whose width in the center axis direction isshown by β (β>4α). As a result, it becomes possible to crystallize asemiconductor film with more efficiency.

It should be noted here that even if the laser lights are made tooverlap each other, there still exist areas in which the energy densitydoes not reach the desired value. In the laser irradiation apparatus ofthe present invention, each region of the synthesized beam spots with alow energy density is shielded by the slit 105, thereby preventing asituation where such a region is irradiated onto the substrate 106. Apositional relation between the beam spot obtained as a result of thesynthesizing and the slit will be described with reference to FIGS. 4Ato 4C.

The slit 105 used in the present invention has a changeable slit widththat is controlled by the computer 110. In FIG. 4A, reference numeral120 designates the shape of the beam spot shown in FIG. 3A that has beenobtained as a result of the synthesizing, while reference numeral 105indicates the slit. In FIG. 4A, there is shown a state where the beamspot 120 is not shielded by the slit.

FIG. 4B shows a state where a beam spot 127 is shielded in part by theslit 105. Also, FIG. 4C shows the distribution of the energy density ofthe beam spot shown in FIG. 4B in the center axis L direction. Incontrast to the case shown in FIG. 3B, each region with a low energydensity is cut by the slit 105.

An area of a semiconductor film irradiated with such a region with a lowenergy density has poor crystallinity. Specifically, in comparison withan area irradiated with a region filled with an energy density, crystalgrains become small or grow in different directions. FIG. 5A shows thescanning path of the beam spot 120 shown in FIG. 3B and a positionalrelation with the pattern of masks. In FIG. 5A, the beam spot 120 isscanned by moving the substrate in the direction shown by an arrow.Reference numeral 122 denotes an area irradiated with a region having adesired energy density. On the other hand, reference numerals 123 and124 each represent an area irradiated with a region whose energy densitydoes not reach the desired value, and the crystal grains in such an areaare smaller than those in the area 122. Further, in the area 123, thecrystal grows in a direction vertical to the substrate. On the otherhand, in the area 124, the crystal grows in a plane parallel to thesubstrate and the crystal grains in this area 124 are smaller than thosein the area 123. Note that the crystallinity in an area irradiated witha region with a low energy density varies depending on the thickness ofa semiconductor film, the kind of a laser, an irradiation condition, andthe like and areas irradiated with a region having a low energy densityare not necessarily classified into the two areas described above.

In FIG. 5A, the areas 123 and 124 overlap patterns 121 of active layersand this is not a preferable situation. As a result, it becomesnecessary to determine the scanning path of the laser lights and thelayout of active layers so that there is prevented a situation where theregions whose energy density is low overlap the active layers or theirchannel formation regions.

In FIG. 5B, there is shown a state where the beam spot 127, whoseregions with a low energy density is shielded, is scanned by moving thesubstrate in the arrow direction. Reference numeral 125 denotes a regionwhose energy density reaches the desired value, and the crystallinity inan area irradiated with this laser light region becomes uniform. Also,in contrast to the case shown in FIG. 5A, the areas 123 and 124irradiated with the regions having a low energy density do not exist orthe widths thereof are reduced in comparison with the case shown in FIG.5A, so that it becomes easier to prevent a situation where the edgeportions of the laser lights overlap the patterns 121 of the activelayers. As described above, each region with a low energy density is cutby providing the slit, so that it becomes possible to reduce limitationsimposed on the scanning path of the laser lights and the layout of theactive layers.

Also, it is possible to change the width of the beam spot whilemaintaining the energy density constant without terminating the outputfrom the laser oscillation apparatuses, which makes it possible toprevent a situation where edges of the laser lights overlap the activelayers or their channel formation regions. Also, there is prevented asituation where the laser lights are irradiated onto unnecessaryportions and the substrate is damaged.

It should be noted here that in FIGS. 5A and 5B, the center axisdirection of the beam spot and the scanning direction are set verticalto each other, although the center axis of the beam spot is notnecessarily required to be set vertical to the scanning direction. Forinstance, the center axis of the beam spot and the scanning directionmay form an acute angle θ_(A) of 45°±35°, more preferably, 45° In thecase where the center axis of the beam spot extends vertically to thescanning direction, efficiency in the processing of a substrate ismaximized. On the other hand, by performing scanning so that the centeraxis of the beam spot after the synthesizing and the scanning directionforms an angle of 45°±35° (preferably, an angle closer to 45°), itbecomes possible to intentionally increase the number of crystal grainsexisting in the active layers and to reduce variations incharacteristics resulting from the orientation of a crystal and crystalgrains in comparison with a case where scanning is performed so that thescanning direction and the center axis of the beam spot are set verticalto each other. Also, in comparison with a case where scanning isperformed so that the scanning direction and the center axis of the beamspot are set vertical to each other, it becomes possible to elongate alaser light irradiation time per substrate.

A positional relation between the slit and the beam spot in the casewhere the center axis of the beam spot is set to form an angle of 45°with the scanning direction will be described with reference to FIGS. 6Aand 6B. Reference numeral 130 denotes a beam spot after the synthesizingand reference numeral 105 represents a slit. The slit 105 does notoverlap the beam spot 130. The arrow indicates the scanning directionand an angle θ with the center axis of the beam spot 130 is maintainedat 45°.

FIG. 6B shows a state where a beam spot 131 is shielded in part by theslit 105 and is reduced in width. In the present invention, the slit 105controls the width Q of the beam spot in a direction vertical to thescanning direction and realizes the uniform irradiation of the laserlights.

Next, the scanning direction of the laser lights on a semiconductor film500 formed to produce a semiconductor device of active matrix type willbe described with reference to FIG. 7A. In FIG. 7A, the portionsurrounded by a broken line 501 corresponds to a portion in which therewill be formed a pixel portion, the portion surrounded by a broken line502 corresponds to a portion in which there will be formed a signal linedriving circuit, and the portion surrounded by a broken line 503corresponds to a portion in which there will be formed a scanning linedriving circuit.

In FIG. 7A, there is shown an example where the laser lights are scannedonly once onto each portion that will become active layers. A substrateis moved in the direction shown by a hollow arrow and the solid-linearrows specify a relative scanning direction of the laser lights. FIG.7B is an enlarged view of a beam spot 507 in the portion 501 in whichthe pixel portion will be formed. Active layers will be formed in thearea irradiated with the laser lights.

Next, the scanning direction of the laser lights on a semiconductor film300 in the case where the laser lights are scanned twice by changing thescanning direction will be described with reference to FIG. 8A. In FIG.8A, the portion surrounded by a broken line 301 corresponds to a portionin which there will be formed a pixel portion, the portion surrounded bya broken line 302 corresponds to a portion in which there will be formeda signal line driving circuit, and the portion surrounded by a brokenline 303 corresponds to a portion in which there will be formed ascanning line driving circuit.

In FIG. 8A, a substrate is moved in the direction shown by hollow arrowsand the solid-line arrows specify relative scanning directions of thelaser lights. In FIG. 8A, laser lights are irradiated onto asemiconductor film in two different scanning directions, the solid-linearrows show a relative scanning direction of the first laser lightirradiation operation, and the broken-line arrows show a relativescanning direction of the second laser light irradiation operation.Also, an active layer is formed in each area at the intersection of thelaser lights irradiated by the first irradiation operation and the laserlights irradiated by the second irradiation operation.

FIG. 8B is an enlarged view of a beam spot 307 during the first scanningoperation, while FIG. 8C is an enlarged view of the beam spot 307 duringthe second scanning operation. Note that in FIGS. 8A to 8C, the relativescanning direction of the first laser light irradiation operation andthe relative scanning direction of the second laser light irradiationoperation form an angle of approximately 90°, although the angle betweenthem is not limited to this.

Also, it is preferable that the laser lights are irradiated so thatthere is prevented a situation where the edge portions of the beam spotsoverlap portions (portions 506 in FIG. 7B and portions 306 in FIGS. 8Band 8C) that correspond to island-like semiconductor films that will beobtained by patterning the semiconductor film after crystallization.

It should be noted here that in FIG. 8A, the laser lights are irradiatedtwice onto all of the pixel portion 301, the signal line driving circuit302, and the scanning line driving circuit 303. However, the presentinvention is not limited to this.

Then, in the present invention, each portion to be scanned with thelaser lights is determined in accordance with the pattern informationconcerning masks inputted into the computer 110. Note that the masks tobe used are selected according to each portion that should becrystallized. In the case where each active layer will be crystallizedin its entirety, for instance, there are used masks for patterning asemiconductor film. On the other hand, in the case where only eachchannel formation region will be crystallized, there are used the masksfor patterning a semiconductor film and masks for performing impuritydoping.

Then, each portion to be scanned with the laser lights is made to coverportions of a semiconductor film to be obtained through patterning aftercrystallization. The computer 110 determines the portion to be scannedwith the laser lights so that at least each portion of the semiconductorfilm to be obtained through the patterning will be crystallized. Also,the computer 110 controls the position control means 108 and 109 so thatthe beam spot, that is, the irradiation position coincides with theportion to be scanned. In this manner, the semiconductor film ispartially crystallized.

In FIG. 9A, there is shown a relation between portions to be scannedwith the laser lights and the masks in the case where the irradiation ofthe laser lights is performed once. Note that in FIG. 9A, the centeraxis of the beam spot extends approximately vertically to the scanningdirection. In FIG. 9B, there is shown a relation between the portions tobe scanned with the laser lights and the masks in the case where thecenter axis of the beam spot and the scanning direction forms an angleof 45°. Reference numeral 510 denotes each island-like semiconductorfilm, which will be obtained through patterning, of a semiconductorfilm, and the portions to be scanned with the laser lights aredetermined so that these island-like semiconductor films 510 are coveredwith the portions to be scanned. Reference numeral 511 represents eachportion to be scanned with the laser lights, with the island-likesemiconductor films 510 being covered with the portions to be scanned.As shown in FIGS. 9A and 9B, in the present invention, the laser lightsare not irradiated onto the entire surface of the semiconductor film butare scanned so that at least each indispensable portion is crystallizedto a minimum.

It should be noted here that in the case where the semiconductor filmafter the crystallization is used as the active layers of TFTs, it ispreferable that the scanning direction of the laser lights is setparallel to the direction in which carriers in channel formation regionsmove.

FIGS. 10A and 10B each show an example of the layout of the active layerof a TFT in the case where the laser lights are irradiated once. FIG.10A shows an active layer in which one channel formation region isprovided and impurity regions 521 and 522 that will become a sourceregion and a drain region are provided so that a channel formationregion 520 is sandwiched therebetween. When the semiconductor film iscrystallized using the laser irradiation apparatus of the presentinvention, the scanning direction of the laser lights is set parallel toa direction in which the carriers in the channel formation region move,as indicated by the arrow. Reference numeral 524 indicates a region ofthe beam spot that has an energy density that is necessary to obtain afavorable crystal. By irradiating the laser lights onto the entiresurface of the active layer, it becomes possible to further enhance thecrystallinity of the active layer.

Also, FIG. 10B shows an active layer that is provided with three channelformation regions. In this drawing, impurity regions 533 and 534 areprovided so that a channel formation region 530 is sandwichedtherebetween. Also, impurity regions 534 and 535 are provided so that achannel formation region 531 is sandwiched therebetween. Further,impurity regions 535 and 536 are provided so that a channel formationregion 532 is sandwiched therebetween. In addition, when thesemiconductor film is crystallized using the laser irradiation apparatusof the present invention, the scanning direction of the laser lights isset parallel to the direction in which carriers in the channel formationregions move, as indicated by the arrow. Note that in FIGS. 10A and 10B,it does not matter whether the scanning of the beam spot is performed bymoving the substrate or is performed using an optical system.Alternatively, the scanning of the beam spot may be performed using bothof the moving of the substrate and the optical system.

Next, a relation between each portion to be scanned by the first laserlight irradiation operation and masks in the case where the laser lightirradiation is performed twice is shown in FIG. 11A. Note that in FIG.11A, the center axis of the beam spot extends approximately verticallyto the scanning direction. Reference numeral 310 denotes eachisland-like semiconductor film, which will be obtained throughpatterning, of the semiconductor film and each portion to be scannedwith the laser lights is determined so that these island-likesemiconductor films 310 will be covered with this portion to be scanned.Reference numeral 311 represents each portion to be scanned with thelaser lights and covers the island-like semiconductor films 310. Asshown in FIG. 11A, in the present invention, during the firstirradiation operation, the laser lights are not irradiated onto theentire surface of the semiconductor film but are scanned so that atleast each indispensable portion is crystallized to a minimum.

Next, FIG. 11B shows a relation between each portion to be scanned bythe laser lights and masks in the case where laser light irradiation isperformed twice and the second laser light irradiation operation isperformed for the semiconductor film shown in FIG. 11A. In FIG. 11B, thescanning direction of the second laser light irradiation operationdiffers from the scanning direction of the first laser light irradiationoperation, with the difference therebetween being 90°. Also, during thesecond laser light irradiation operation, each portion to be scanningwith the laser lights is determined so that each portion 310 that willbecome an island-like semiconductor film will be covered with theportion to be scanned. Also, during the second laser light irradiationoperation, it is required to change the direction of the slit in a likemanner. Reference numeral 313 denotes each portion to be scanned withthe laser lights during the second laser light irradiation operation andcovers the island-like semiconductor films 310. As shown in FIG. 11B, inthe present invention, during the second laser light irradiationoperation, the laser lights are not irradiated onto the entire surfaceof the semiconductor film but are scanned so that at least eachindispensable portion is crystallized to a minimum.

Accordingly, each portion 310 that will become an island-likesemiconductor film is irradiated twice by laser lights while changingthe scanning direction, so that the crystallinity is further enhanced.Also, the laser lights are not irradiated onto the entire surface of thesubstrate but are irradiated onto a minimum portion required tocrystallize the portions, which are determined by the masks, of thesemiconductor film. This makes it possible to suppress a time taken toprocess one substrate and to enhance the efficiency in the processing ofa substrate.

It should be noted here that in FIGS. 11A and 11B, during both of thefirst and second laser light irradiation operations, the laser lightsare not irradiated onto the entire surface of the semiconductor film butare irradiated onto a minimum portion required to crystallize theportions, which are determined by the masks, of the semiconductor film.However, the present invention is not limited to this construction andthe laser lights may be irradiated onto the entire surface of thesemiconductor film during the first laser light irradiation operationand the laser lights may be partially irradiated during the second laserlight irradiation operation. Conversely, the laser lights may bepartially irradiated during the first laser light irradiation operationand the laser lights may be irradiated onto the entire surface of thesubstrate during the second laser light irradiation operation. FIG. 12Ashows a state during the first laser light irradiation operation wherethe laser lights are irradiated onto the entire surface of thesemiconductor film, while FIG. 12B shows a state during the second laserlight irradiation operation where the laser lights are irradiated ontothe semiconductor film shown in FIG. 12A. Reference numeral 314 denoteseach portion to be scanned with the laser lights during the first laserlight irradiation operation, with the entire surface of thesemiconductor film being covered with the portion to be scanned. Also,reference numeral 315 indicates the shape of each island-likesemiconductor film to be obtained through patterning, with theisland-like semiconductor film being arranged at a position at whichthis semiconductor film does not overlap the edges of the portion to bescanned with the laser lights during the first laser light irradiationoperation. Also, reference numeral 316 represents each portion to bescanned with the laser lights during the second laser light irradiationoperation, with the island-like semiconductor films 315 to be obtainedthrough patterning being covered with the portion to be scanned.Further, the laser lights are not irradiated onto the entire surface ofthe semiconductor film during the second laser light irradiationoperation but are partially irradiated so that at least the island-likesemiconductor films 315 are irradiated with the laser lights.

It should be noted here that in the case where the semiconductor filmafter the crystallization is used as the active layers of TFTs, it ispreferable that the scanning direction of the laser lights is setparallel to the direction, in which carriers in channel formationregions move, during either of the first laser light irradiationoperation and the second laser light irradiation operation.

FIGS. 13A and 13B each show an example of an active layer of a TFT. FIG.13A shows an active layer that is provided with one channel formationregion and impurity regions 321 and 322 that will become a source regionand a drain region are provided so that a channel formation region 320is sandwiched therebetween. When the semiconductor film is crystallizedusing the laser irradiation apparatus of the present invention, thescanning direction of the laser lights during the first or second laserlight irradiation operation is set parallel to a direction in whichcarriers in the channel formation region move, as shown by the arrow.Note that in FIGS. 13A and 13B, it does not matter whether the scanningof the beam spot is performed by moving the substrate or is performedusing an optical system. Alternatively, the scanning of the beam spotmay be performed using both of the moving of the substrate and theoptical system.

Reference numeral 323 denotes a region, whose energy density fallswithin a range of values that are necessary to obtain the favorablecrystal, of the beam spot of the laser lights during the first laserlight irradiation operation, with the beam spot being scanned in thedirection shown by the solid-line arrow. By irradiating the region 323of the laser lights onto the whole of the active layer, it becomespossible to further enhance the crystallinity of the active layer.

Also, reference numeral 326 denotes a region, whose energy density fallswithin the range of values that are necessary to obtain the favorablecrystal, of the beam spot of the laser lights during the second laserlight irradiation operation, with this beam spot being scanned in thedirection shown by the broken-line arrow. As shown in FIG. 13A, thescanning direction during the first laser light irradiation operationand the scanning direction during the second laser light irradiationoperation differ from each other. By irradiating the region 326 of thelaser lights onto the whole of the active layer, it becomes possible tofurther enhance the crystallinity of the active layer.

Also, FIG. 13B shows an active layer provided with three channelformation regions. In this drawing, impurity regions 333 and 334 areprovided so that a channel formation region 330 is sandwichedtherebetween. Also, impurity regions 334 and 335 are provided so that achannel formation region 331 is sandwiched therebetween. Further,impurity regions 335 and 336 are provided so that a channel formationregion 332 is sandwiched therebetween. In addition, the laser lightsirradiated by the first laser light irradiation operation are scanned inthe direction shown by the solid-line arrow, the laser lights irradiatedby the second laser light irradiation operation are scanned in thedirection shown by the broken-line arrow, and the scanning directionduring the first or second laser light irradiation operation is setparallel to the direction in which the carriers in the channel formationregions move.

It should be noted here that it is sufficient that the scanningdirection of the laser lights is set parallel to the moving direction ofthe carriers during either of the first and second laser lightirradiation operations, although it is more preferable that the scanningdirection of laser lights having a higher energy density is set parallelto the moving direction because the direction in which a crystal growsis more strongly influenced by the scanning direction of the laserlights having a higher energy density.

Also, in the case where the major axis direction of a beam spot having alinear or elliptic shape does not extend vertically to the scanningdirection, it is not necessarily required that the moving direction ofthe carriers coincides with the scanning direction. In this case, it isconceived that a crystal grows in a direction vertical to the major axisdirection, so that it is preferable that this direction is made tocoincide with the moving direction of the carriers.

A relation between the scanning direction of laser lights on asemiconductor film formed to produce a semiconductor device of activematrix type and the layout of active layers in respective circuits inthe case where the irradiation of the laser lights is performed twicewill be described with reference to FIG. 14.

In FIG. 14, a semiconductor film 850 is formed on a substrate. Theportion surrounded by a broken line 853 is a portion in which there willbe formed a pixel portion, and portions 856 that will become a pluralityof active layers are provided in this pixel portion 853. The portionsurrounded by a broken line 854 is a portion in which there will beformed a signal line driving circuit, and portions 857 that will becomea plurality of active layers are provided in this signal line drivingcircuit 854. The portion surrounded by a broken line 855 is a portion inwhich there will be formed a scanning line driving circuit, and portions858 that will become a plurality of active layers are provided in thisscanning line driving circuit 855.

It should be noted here that the portions 856, 857, and 858 that willbecome active layers possessed by respective circuits have a small size(in units of several ten μm) in actual cases, although these portionsare intentionally illustrated using a size that is larger than the realsize in FIG. 14 in order to make it easier to understand the drawing.The portions 856, 857, and 858 that will become the active layerspossessed by respective circuits are laid out so that the directions inwhich carriers in their channel formation regions move are broadlydivided into two directions (the first direction and the seconddirection).

Reference numeral 851 denotes each portion that will be crystallized bythe first laser light irradiation operation and covers all of theportions 856, 857, and 858 that will become the active layers. Also, thefirst laser light irradiation operation is performed so that itsscanning direction becomes parallel to the first direction.

Also, reference numeral 852 represents each portion that will becrystallized by the second laser light irradiation operation. Thescanning direction during the second laser light irradiation operationdiffers from the scanning direction of the first laser light irradiationoperation and becomes parallel to the second direction. Further, thelaser lights irradiated by the second scanning operation do not coverall of the portions 856, 857, and 858 that will become the active layersbut cover only each active layer whose moving direction of carriers inthe channel formation region is parallel to the second direction. InFIG. 14, the second laser light irradiation operation is performed onlyon each active layer in which the moving direction of carriers in itschannel formation region becomes parallel to the scanning direction ofthe second laser light irradiation operation, among the plurality ofactive layers 858.

It should be noted here that in order to determine each portion to bescanned with the laser lights, it is necessary to form, on thesemiconductor film, markers for determining the positions of masks withrespect to the semiconductor film. FIGS. 15A and 15B show positions atwhich the markers will be formed on a semiconductor film formed toproduce a semiconductor device of active matrix type. Note that FIG. 15Ashows an example where one semiconductor device will be produced fromone substrate, while FIG. 15B shows an example where four semiconductordevices will be produced from one substrate.

In FIG. 15A, reference numeral 540 denotes a semiconductor film formedon a substrate, the portion surrounded by a broken line 541 correspondsto a portion (hereinafter referred to as the “pixel-portion-formingportion” in which there will be formed a pixel portion, the portionsurrounded by a broken line 542 corresponds to a portion (hereinafterreferred to as the “signal-line-driving-circuit-forming portion” inwhich there will be formed a signal line driving circuit, and theportion surrounded by a broken line 543 corresponds to a portion(hereinafter referred to as the “scanning-line-driving-circuit-formingportion”) in which there will be formed a scanning line driving circuit.Reference numeral 544 represents portions (marker-forming portions) inwhich there will be formed the markers, with these portions beingprovided and positioned at four corners of the semiconductor film.

It should be noted here that the four marker-forming portions 544 arerespectively provided at the four corners in FIG. 15A, although thepresent invention is not limited to this construction. The positions ofthe marker-forming portions and the number thereof are not limited tothe form described above so long as it is possible to align the portionsof the semiconductor film which will be scanned with the laser lightswith the masks for patterning the semiconductor film.

In FIG. 15B, reference numeral 550 denotes a semiconductor film formedon a substrate and broken lines 551 indicate scribe lines along whichthe substrate will be divided in a subsequent step. In FIG. 15B, it ispossible to produce four semiconductor devices by dividing the substratealong the scribe lines 551. Note that the number of semiconductordevices obtained through the division is not limited to this.

Reference numeral 552 represents marker-forming portions, with theseportions being provided and positioned at four corners of thesemiconductor film. It should be noted here that the four marker-formingportions 552 are respectively provided at the four corners in FIG. 15B,although the present invention is not limited to this construction. Thepositions of the marker-forming portions and the number thereof are notlimited to the form described above so long as it is possible to alignthe portions of the semiconductor film which will be scanned with thelaser lights, with the masks for patterning the semiconductor film.

It is possible to cite a YAG laser, CO₂ laser, and the like asrepresentative examples of the laser used to form the markers. Needlessto say, however, it is possible to form the markers using another laser.

Next, there will be described a production flow of a semiconductordevice using the laser irradiation apparatus of the present invention.

A production flow in the case where the irradiation of the laser lightsis performed once is shown in FIG. 16 as a flowchart. First, there isperformed the designing of a semiconductor device using CAD. Then,information concerning the shape of masks for patterning the designedsemiconductor film is inputted into the computer possessed by the laserirradiation apparatus. On the other hand, after an amorphoussemiconductor film is formed on a substrate, the substrate, on which theamorphous semiconductor film has been formed, is placed in the laserirradiation apparatus. Then, the markers are formed on the surface ofthe semiconductor film using a laser.

On the basis of the mask information inputted by the computer, eachportion to be scanned with the laser lights is determined with referenceto the positions of the markers. Then, with reference to the formedmarkers, the laser lights are irradiated onto the portion to be scannedwith the laser lights, thereby partially crystallizing the semiconductorfilm.

Then, after the irradiation of the laser lights, a polycrystallinesemiconductor film obtained by the irradiation of the laser lights ispatterned and etched, thereby forming island-like semiconductor films.Following this, there is performed a step for producing TFTs from theseisland-like semiconductor films. The concrete step for producing theTFTs varies depending on the shape of the TFTs. Representatively,however, gate insulating films are formed and impurity regions areformed in the island-like semiconductor films. Then, interlayerinsulating films are formed so as to cover the gate insulating films andgate electrodes, and contact holes are established in the interlayerinsulating films. In this manner, there are obtained exposed parts ofthe impurity regions. Then, wiring is formed on the interlayerinsulating films so as to contact the impurity regions through thecontact holes.

Next, a production flow in the case where the irradiation of the laserlights is performed twice is shown in FIG. 17 as a flowchart. First,there is performed the designing of a semiconductor device using CAD.Then, information concerning the shape of masks for patterning thedesigned semiconductor film is inputted into the computer possessed bythe laser irradiation apparatus. On the other hand, after an amorphoussemiconductor film is formed on a substrate, the substrate, on which theamorphous semiconductor film has been formed, is placed in the laserirradiation apparatus. Then, markers are formed on the surface of thesemiconductor film using a laser.

On the basis of the mask information inputted by the computer, eachportion to be scanned with the laser lights during the first and secondlaser light irradiation operations is determined with reference to thepositions of the markers. Note that the portion to be scanned with thelaser lights during the second laser light irradiation operation variesdepending on an angle between the scanning direction of the first laserlight irradiation operation and the scanning direction of the secondlaser light irradiation operation. It does not matter whether the anglebetween the scanning direction of the first laser light irradiationoperation and the scanning direction of the second laser lightirradiation operation is presorted in a memory or the like or ismanually inputted as occasion demands. Then, with reference to theformed markers, the laser lights are irradiated onto the portion to bescanned with the laser lights during the first laser light irradiationoperation, thereby partially crystallizing the semiconductor film.

Next, the scanning direction of the laser lights is changed by apredetermined value using the first means, the direction of the slit isalso changed in accordance with the changing of the scanning direction,and there is performed the second laser light irradiation operation. Inthis manner, the semiconductor film is partially crystallized.

Then, after the irradiation of the laser lights, a polycrystallinesemiconductor film obtained by the irradiation of the laser lights ispatterned and etched, thereby forming island-like semiconductor films.Following this, there is performed a step for producing TFTs from theseisland-like semiconductor films. The concrete step for producing theTFTs varies depending on the shape of the TFTs. Representatively,however, gate insulating films are formed and impurity regions areformed in the island-like semiconductor films. Then, interlayerinsulating films are formed so as to cover the gate insulating films andgate electrodes, and contact holes are established in the interlayerinsulating films. In this manner, there are obtained exposed parts ofthe impurity regions. Then, wiring is formed on the interlayerinsulating films so as to contact the impurity regions through thecontact holes.

It should be noted here that as a comparison example, a conventionalflow for producing a semiconductor device is shown in FIG. 18 as aflowchart. As shown in FIG. 18, the designing of masks for asemiconductor device is performed using CAD. On the other hand, anamorphous semiconductor film is formed on a substrate and the substrate,on which the amorphous semiconductor film has been formed, is placed ina laser irradiation apparatus. Then, laser lights are scanned andirradiated onto the entire surface of the amorphous semiconductor film,thereby crystallizing the entire surface of the amorphous semiconductorfilm. Then, markers are formed in a polycrystalline semiconductor filmobtained through the crystallization and island-like semiconductor filmsare formed by patterning the polycrystalline semiconductor film withreference to the markers. Then, TFTs are produced using the island-likesemiconductor films.

As described above, in contrast to a conventional case such as the caseshown in FIG. 18, in the present invention, markers are formed using alaser light prior to the crystallization of an amorphous semiconductorfilm. Then, laser lights are scanned in accordance with informationconcerning masks for patterning the semiconductor film.

With the construction described above, it becomes possible to save atime taken to irradiate the laser lights onto each portion to be removedthrough patterning after the crystallization of the semiconductor film,which makes it possible to shorten a time taken to irradiate the laserlights and also to improve the speed at which a substrate is processed.

It should be noted here that there may be included a step forcrystallizing the semiconductor film using a catalyst. In the case wherea catalytic element is used, it is preferable that there is used thetechnique disclosed in JP 07-130652 A or JP 08-78329 A.

If a step whereby a catalyst is used for crystallizing a semiconductorfilm is included, it includes a step whereby an amorphous semiconductorfilm is formed and then crystallized using Ni (NiSPC). For instance, inthe case where there is used the technique disclosed in JP 07-130652 A,a nickel-containing layer is formed by applying a nickel acetatesolution containing 10 ppm nickel on a weight basis onto the amorphoussemiconductor film. Then, after a dehydrogenation step is performed forone hour at 500° C., crystallization is performed by performing heattreatment for 4 to 12 hours at 500 to 650° C. (for eight hours at 550°C., for instance). Note that, as to a usable catalytic element, anelement such as germanium (Ge), iron (Fe), palladium (Pd), tin (Sn),lead (Pd), cobalt (Co), platinum (Pt), copper (Cu), or gold (Au) may beused in addition to nickel (Ni).

Also, the crystallinity of the semiconductor film crystallized by NiSPCis further enhanced using the irradiation of laser lights. Apolycrystalline semiconductor film obtained by the laser lightirradiation contains a catalytic element and there is performed a step(gettering) for removing the catalytic element from the crystallinesemiconductor film after the laser light irradiation. It is possible touse the technique disclosed in JP 10-135468 A or JP 10-135469 A toperform the gettering.

In more detail, phosphorus is added to a part of the polycrystallinesemiconductor film obtained after the laser irradiation and heattreatment is performed in a nitrogen atmosphere for 5 to 24 hours at 550to 800° C. (for 12 hours at 600° C., for instance). As a result of thisprocessing, the region of the polycrystalline semiconductor film, inwhich there has been added the phosphorus, functions as a gettering siteand it becomes possible to segregate the phosphorus existing in thepolycrystalline semiconductor film in the region in which the phosphorushas been added. Following this, by removing the region of thepolycrystalline semiconductor film, in which the phosphorus has beenadded, through patterning, it is possible to obtain island-likesemiconductor films in which the density of the catalytic element isreduced to 1×10¹⁷ atoms/cm³ or below, preferably, around 1×10¹⁶atms/cm³.

As described above, according to the present invention, laser lights arenot scanned and irradiated on the entire surface of the semiconductorfilm but are scanned so that it is possible to crystallize at least eachindispensable portion to a minimum. With the construction describedabove, it becomes possible to save on time taken to irradiate the laserlights onto each portion to be removed through patterning after thecrystallization of the semiconductor film and to significantly shorten atime taken to process one substrate.

EMBODIMENTS

Hereinafter, there will be described embodiments of the presentinvention.

Embodiment 1

The crystalline semiconductor film formed by irradiation of laser lightcomprises aggregations of a plurality of crystal grains. The crystalgrains have random positions and sizes and hence, it is difficult toform a crystalline semiconductor film with specified position and sizeof crystal grains. Accordingly, the active layers formed by patterningthe crystalline semiconductor film into the islands may contain graininterfaces (grain boundaries).

Unlike crystal grains, the grain boundaries contains therein an infinitenumber of recombination centers and trapping centers associated withamorphous structure and crystal defects. It is known that carrierstrapped in the trapping centers increase the potential of the grainboundaries, which form barriers against carriers, so that the carriersare reduced in current transportability. Therefore, the grain boundariespresent in the active layer of a TFT, or particularly in the channelforming region, will exert serious effects on the TFT characteristics,such as a significant decrease in the mobility of the TFT, or anincreased OFF current due to current flow through the grain boundaries.Furthermore, a plurality of TFTs, fabricated based on the premise thatthe same characteristics can be obtained, will encounter variedcharacteristics due to the presence of the grain boundaries in theactive layers.

The reason why the laser irradiation on the semiconductor film producescrystal grains of random sizes at random positions is as follows. Thatis, a certain length of time is taken before the formation ofsolid-phase nuclei takes place in a semiconductor film completely moltenby the laser irradiation. With the passage of time, an infinite numberof crystal nuclei occur in the fully molten region and crystals growfrom the respective nuclei. Since the crystal nuclei occur at randompositions, an irregular distribution of the crystal nuclei results. Thecrystal grains grow to collide with one another, where the crystal growprocess terminates. Consequently, the crystal grains have randompositions and sizes.

On the other hand, there has been proposed a method wherein thecrystalline semiconductor film is formed by locally melting thesemiconductor film instead of melting the whole semiconductor film. Inthis case, the laser irradiation produces a portion where thesemiconductor film is completely molten and a portion where asolid-phase semiconductor region is present, the solid-phasesemiconductor region acting as the crystal nuclei from which grainsstart growing. Nucleation in the completely molten region requires acertain length of time. During the lapse of time until the occurrence ofnucleation in the completely molten region, the grains grow from thesolid-phase semiconductor region, as the crystal nuclei, in a horizontaldirection (hereinafter referred to as “lateral direction”) with respectto the surface of the semiconductor film. Accordingly, the grains growin lengths no less than dozens times the thickness of the semiconductorfilm. After the lapse of some time, crystal grains in the completelymolten region also start crystallizing and collide with the grainsgrowing from the nuclei, where the lateral crystal grow terminates.Hereinafter, this phenomenon will be referred to as “superlateralgrowth”.

The superlateral growth process provides relatively larger crystalgrains, correspondingly reducing the number of grain boundaries.Unfortunately, laser light for effecting the superlateral growth isquite limited in the range of energy. In addition, it is difficult tocontrol the location where large grains are formed. Furthermore, otherregions than the large grains are minor crystal regions containing aninfinite number of nuclei or amorphous regions and hence, irregularcrystal sizes result.

It is contemplated that a location- and direction-controlled graingrowth process is practicable if laser light in such an energy range asto completely melt the semiconductor film is used and a lateraltemperature gradient can be controlled. A variety of attempts have beenmade to realize this process.

For instance, James. S. Im et al at Colombia University have proposedSequential Lateral Solidification method (hereinafter referred to as SLSmethod) for effecting the superlateral growth at arbitrary locations.The SLS process is arranged such that crystallization is performed bytranslating a slit mask by a distance of superlateral growth (about 0.75μm) at each shot of the laser light.

This embodiment illustrates an example where the SLS process is appliedto the invention.

Firstly, a first laser light is irradiated on a semiconductor film. Inthis case, a pulse oscillation type laser and a continuous wave typelaser are both usable. The first laser light is irradiated exclusivelyon an area defined by a mask. Although the energy density of the firstlaser light varies depending upon the thickness of the semiconductorfilm, the first laser light may have such a degree of energy density asto enhance the crystallinity of the area defined by the mask.

Next, the scanning direction is changed and a second laser light isirradiated on the area defined by the mask. The second laser light isemitted from the pulse oscillation type laser and is irradiated at suchan energy density as to melt a local portion of the area defined by themask to the full depth of the semiconductor film.

FIG. 19A schematically shows a state of the semiconductor filmimmediately after a first shot of the second laser light. Asemiconductor film 802 is equivalent to the area enhanced incrystallinity by the irradiation of the first laser light. Theirradiation of the second laser light locally melts the semiconductorfilm 802 to the full depth thereof at the portion thereof under a beamspot 801.

At this time, the semiconductor film 802 is fully molten at its portionunder the beam spot 801 whereas a portion out of the beam spot is notmolten or molten at much lower temperature than the beam spot portion.Therefore, an edge of the beam spot portion forms seed grains, whichgrow laterally from the edge of the beam spot portion toward center asindicated by arrows in the figure.

As the crystal growth proceeds with time, the grains collide with grainsfrom seed grains produced in the fully molten portion or with thegrowing seed grains on the opposite side so that the grain growth stopsat a central portion 803 of the beam spot. FIG. 19B schematically showsa state of the semiconductor film at the termination of the crystalgrowth. The semiconductor film has an irregular surface at the centralportion 803 of the beam spot, where a greater number of fine crystalsare present than in the other portion or the crystal grains collide withone another.

Next, a second shot of the second laser light is applied. The secondshot is applied to place slightly shifted from the beam spot of thefirst shot. FIG. 19C schematically shows a state of the semiconductorfilm immediately after the second shot. In FIG. 19C, a beam spot of thesecond shot is shifted from the portion 801 under the beam spot of thefirst shot to a degree that the beam spot of the second shot covers thecentral portion 803 formed by the first shot.

At this time, a portion under a beam spot 804 of the second shot isfully molten whereas a portion out of the beam spot is not molten ormolten at much lower temperature than the beam spot portion. Therefore,an edge of the beam spot portion forms seed grains, which grow laterallyfrom the edge of the beam spot portion toward center as indicated byarrows in the figure. At this time, out of the portion 801 crystallizedby the first shot, a part unirradiated by the beam spot of the secondshot forms seed grains so that the laterally grown grains due to thefirst shot further grow along the scanning direction.

As the crystal growth proceeds with time, the grains collide with grainsfrom seed grains produced in the fully molten portion or with thegrowing seed grains on the opposite side so that the grain growth stopsat a central portion 805 of the beam spot of the second shot. FIG. 19Dschematically shows a state of the semiconductor film at the terminationof the crystal growth. The semiconductor film has an irregular surfaceat the central portion 805 of the beam spot, where a greater number offine crystals are present than in the other portion or the crystalgrains collide with one another.

In a similar manner, a third shot and the subsequent shots are appliedas slightly shifting beam spots thereby accomplishing the crystal growthextending in parallel with the scanning direction, as shown in FIG. 19E.

According to the above arrangement, the local crystallization can beaccomplished while controlling the location and size of the crystalgrains.

Next, description is made on another embodiment than that of FIG. 19,which applies the SLS process to the invention.

Firstly, a first laser light is irradiated on a semiconductor film. Inthis case, a pulse oscillation type laser and a continuous wave typelaser are both usable. The first laser light is irradiated exclusivelyon an area defined by a mask. Although the energy density of the firstlaser light varies depending upon the thickness of the semiconductorfilm, the first laser light may have such a degree of energy density asto enhance the crystallinity of the area defined by the mask.

Next, the scanning direction is changed and a second laser light isirradiated on the area defined by the mask. The second laser light isemitted from the pulse oscillation type laser and irradiated at such anenergy density as to melt a local portion of the area defined by themask to the full depth of the semiconductor film.

FIG. 20A schematically shows a state of the semiconductor filmimmediately after the first shot of the second laser light. Asemiconductor film 812 is equivalent to the area enhanced incrystallinity by the irradiation of the first laser light. Theirradiation of the second laser light locally melts the semiconductorfilm 812 to the full depth thereof at the portion thereof under a beamspot 811. An edge of the beam spot portion forms seed grains, which growlaterally from the edge of the beam spot portion toward center asindicated by arrows in the figure.

As the crystal growth proceeds with time, the grains collide with grainsfrom seed grains produced in the fully molten portion or with thegrowing seed grains on the opposite side so that the grain growth stopsat a central portion 813 of the beam spot. FIG. 20B schematically showsa state of the semiconductor film at the termination of the crystalgrowth. The semiconductor film has an irregular surface at the centralportion 813 of the beam spot, where a greater number of fine crystalsare present than in the other portion or the crystal grains collide withone another.

Next, a second shot of the second laser light is applied. The secondshot is applied to place slightly shifted from the beam spot of thefirst spot. FIG. 20C schematically shows a state of the semiconductorfilm immediately after the second shot. A beam spot of the second shotis shifted from the portion 811 under the beam spot of the first shot.In FIG. 20C, a beam spot of the second shot does not cover the centralportion 813 formed by the first shot, shifted therefrom to a degree thatthe beam spot of the second shot overlaps a part of the beam spot of thefirst shot.

An edge of the portion under the beam spot of the second shot forms seedgrains, which grow laterally from the edge of the beam spot portiontoward center as indicated by arrows in the figure. At this time, out ofthe portion 811 crystallized by the first shot, a part unirradiated bythe second shot forms seed grains so that the laterally grown grains dueto the first shot further grow along the scanning direction.

As the crystal growth proceeds with time, the grains collide with grainsfrom seed grains produced in the fully molten portion or with thegrowing seed grains on the opposite side so that the grain growth stopsat a central portion 815 of the beam spot of the second shot. FIG. 20Dschematically shows a state of the semiconductor film at the terminationof the crystal growth. The semiconductor film has an irregular surfaceat the central portion 815 of the beam spot, where a greater number offine crystals are present than in the other portion or the crystalgrains collide with one another.

In a similar manner, a third shot and the subsequent shots are appliedas slightly shifting beam spots thereby accomplishing the crystal growthextending in parallel with the scanning direction, as shown in FIG. 20E.According to the above arrangement, the local crystallization can beaccomplished while controlling the location and size of the crystalgrains.

The central portions of the beam spots remain in the crystals formed bythe irradiation method shown in FIG. 20. Since the center of the beamspot does not present a favorable crystallinity, it is preferred to layout the active layers in a manner to preclude the beam spot centers fromthe channel forming regions or more preferably from the active layers.

In the both laser irradiation methods shown in FIGS. 19 and 20, thechannel forming regions contain a reduced number of grain boundaries ifthe active layers are laid out in a manner that the crystal grains growin parallel with the direction of carrier movement in the channelforming regions. This leads to an increased carrier mobility and adecreased OFF current. If, on the other hand, the active layers are laidout in a manner that the crystal grains grow in an angled directionrelative to the direction of carrier movement in the channel formingregions rather than in parallel therewith, the channel forming regionscontain an increased number of grain boundaries. According to acomparison among plural active layers, however, the individual activelayers have a smaller difference percentage of the total grainboundaries in the channel forming region, leading to decreasedvariations of the mobility and OFF current of the resultant TFTs.

Although the embodiment uses the SLS process in the radiation of thesecond laser light, the embodiment is not limited to this arrangement.For instance, a first laser irradiation may be performed forcrystallization using the SLS process, and a second laser irradiationmay be performed using a pulse oscillation laser thereby eliminatingdefects in the crystal grains formed by the first laser irradiation andfurther enhancing crystallinity. The pulse oscillation laser generallyhas a higher energy density than a continuous wave laser and provides arelatively larger beam spot, thus reducing the processing time persubstrate and achieving a higher processing efficiency.

In this embodiment, an example that the laser light is irradiated twice,however, the laser light may be irradiated only once.

It is noted that the embodiment may employ a mask for shaping the beamspot of the laser light in order to define a region for nucleation.Usable lasers include, but not limited to, pulse oscillation typeexcimer lasers, YLF lasers and the like.

Embodiment 2

In this embodiment, description is made on an optical system foroverlapping beam spot.

FIGS. 21A and 21B illustrate exemplary optical systems according to theembodiment. FIG. 21A shows a side view an optical system of the laserirradiation equipment of the present invention. FIG. 21B shows a sideview that is viewed along the direction of the arrow B in the FIG. 21A.FIG. 21A shows a side view that is viewed along the direction of thearrow A in FIG. 21B.

FIG. 21 shows an optical system which is adopted synthesize the fourbeam spots into a single beam spot. In this embodiment, the number ofbeam spot for synthesizing is not limited to this, the number may rangebetween 2 and 8 (inclusive).

Reference numerals 401 to 405 are cylindrical lenses, not shown in FIG.21. The optical system of this embodiment includes six cylindricallenses. Reference numeral 410 is a slit. FIG. 22 shows a vertical viewof optical system shown in FIG. 21. Laser beam pass through therespective cylindrical lenses 403 to 406 from the different laseroscillation devices.

The laser beams shaped by the cylindrical lenses 403, 405 enter thecylindrical lens 401. The entered laser beams are shaped by thecylindrical lenses, and enter to the slit 410 to be shaped again andimpinge upon the irradiation object 400. On the other hand, the laserbeams shaped by the cylindrical lenses 404, 406 enter the cylindricallens 402. The entered laser beams are shaped by the cylindrical lenses,and enter to the slit 410 to be shaped again and impinge upon theirradiation object 400.

The beam spots of the laser beams on the irradiation object 400 arepartially superpositioned on each other so as to be synthesized into asingle beam spot.

A focal length of the cylindrical lenses 401, 402 closest to theirradiation object 400 is defined to be 20 mm, and a focal length of thecylindrical lenses 403 to 406 is defined to be 150 mm. In thisembodiment, the cylindrical lenses 401, 402 are so positioned as toapply the laser beams to the irradiation object 400 at an incidenceangle of 25° (an incident angle θ₁), whereas the cylindrical lenses 403to 406 are so positioned as to apply the laser beams to the cylindricallenses 401, 402 at an incidence angle of 10° (an incident angle θ₂).

A focal length and incidence angle of each lens may properly be definedby the designer. Further, the number of cylindrical lenses is notlimited to this and the optical system used is not limited tocylindrical lenses. It is sufficient that in the present invention,there is used an optical system that is capable of processing the beamspot of a laser light oscillated from each laser oscillation apparatusso that there is obtained a shape and energy density suited for thecrystallization of a semiconductor film and of synthesizing the beamspots of all laser lights into single beam spot by having the beam spotsoverlap each other.

It should be noted here that in this embodiment, there has beendescribed an example where four beam spots are synthesized. In thiscase, there are provided four cylindrical lenses, which respectivelycorrespond to four laser oscillation apparatuses, and two cylindricallenses that correspond to the four cylindrical lenses. In the case wherebeam spots, whose number is n (n=2, 4, 6, or 8), are combined, there areprovided n cylindrical lenses, which respectively correspond to n laseroscillation apparatuses, and n/2 cylindrical lenses that correspond tothe n cylindrical lenses. In the case where beam spots, whose number isn (n=3, 5, or 7), are combined, there are provided n cylindrical lenses,which respectively correspond to n laser oscillation apparatuses, and(n+1)/2 cylindrical lenses that correspond to the n cylindrical lenses.

Next, a description is made on an optical system of the laserirradiation equipment of the present invention using eight laseroscillation devices.

FIGS. 23, 24 illustrate exemplary optical systems according to theembodiment. FIG. 23 shows a side view an optical system of the laserirradiation equipment of the present invention. FIG. 24 shows a sideview that is viewed along the direction of the arrow B in the FIG. 23.FIG. 23 shows a side view that is viewed along the direction of thearrow A in FIG. 24.

FIGS. 23, 24 show an optical system which is adopted synthesize theeight beam spots into a single beam spot. In this embodiment, the numberof beam spot for synthesizing is not limited to this, the number mayrange between 2 and 8 (inclusive).

Reference numerals 441 to 450 are cylindrical lenses, not shown in FIGS.23, 24. The optical system of this embodiment includes twelvecylindrical lenses 441 to 452. Reference numerals 460, 461 are slits.FIG. 25 shows a vertical view of optical system shown in FIGS. 23, 24.Laser beams pass through the respective cylindrical lenses 441 to 444from the different laser oscillation devices.

The laser beams shaped by the cylindrical lenses 450, 445 enter thecylindrical lens 441. The entered laser beams are shaped by thecylindrical lens 441, and enter to the slit 460 to be shaped again andimpinge upon the irradiation object 440. The laser beams shaped by thecylindrical 451, 446 enter the cylindrical lens 442. The entered laserbeams are shaped by the cylindrical lens 442, and enter to the slit 460to be shaped again and impinge upon the irradiation object 440. Thelaser beams shaped by the cylindrical lenses 449, 447 enter thecylindrical lens 443. The entered laser beams are shaped by thecylindrical lens 443, and enter to the slit 461 to be shaped again andimpinge upon the irradiation object 440. The laser beams shaped by thecylindrical lenses 452, 448 enter the cylindrical lens 444. The enteredlaser beams are shaped by the cylindrical lens 444, and enter to theslit 461 to be shaped again and impinge upon the irradiation object 440.

The beam spots of the laser beams on the irradiation object 440 arepartially superpositioned on each other so as to be synthesized into asingle beam spot.

A focal length of the cylindrical lenses 441 to 444 closest to theirradiation object 440 is defined to be 20 mm, and a focal length of thecylindrical lenses 445 to 452 is defined to be 150 mm. In thisembodiment, the cylindrical lenses 441 to 444 are so positioned as toapply the laser beams to the irradiation object 440 at an incidenceangle of 25° (an incident angle θ₁), whereas the cylindrical lenses 445to 452 are so positioned as to apply the laser beams to the cylindricallenses 441 to 444 at an incidence angle of 10° (an incident angle θ₂).

A focal length and incidence angle of each lens may properly be definedby the designer. Further, the number of cylindrical lenses is notlimited to this and the optical system for using is not limited tocylindrical lenses. It is sufficient that in the present invention,there is used an optical system that is capable of processing the beamspot of a laser light oscillated from each laser oscillation apparatusso that there is obtained a shape and energy density suited for thecrystallization of a semiconductor film and of synthesizing the beamspots of all laser lights into single beam spot by having the beam spotsoverlap each other.

In this embodiment, an example of synthesizing eight beam spots isdescribed. In this case, there are eight cylindrical lensescorresponding to the respective eight laser oscillation devices, andfour cylindrical lenses corresponding to the respective eightcylindrical lenses.

In a case where 5 or more beam spots are synthesized, it is preferred inthe light of the location of the optical system or interference that thefifth or the subsequent laser beam may be irradiated from the oppositeside of the substrate. Thus, the substrate must have light transmission.

To prevent the returning light from tracing back to the light path, itis preferable that the incident light to the substrate is kept more than0°, no less than 90°.

Assumed that a plane perpendicular to an irradiation face and includingeither a shorter side or a longer side of say, a rectangular beam spotof each laser beam is defined as an incidence plane to be realized theuniform laser beam irradiation. It is desirable that the incidence angleθ of the laser beam satisfies θ≧arctan(W/2d) where W denotes a length ofthe shorter or longer side included in the incidence plane, and ddenotes a thickness of the substrate disposed at the irradiation faceand being transparent to the laser beam. This logic needs to be realizedabout each laser beam before synthesized. In a case where a path of alaser beam is out of the incidence plane, the incidence angle θ thereofis defined by that of a laser beam having its path on the incidenceplane. Irradiating the laser beam at this incidence angle θ providesuniform laser radiation free from interference between light reflectedby the surface of the substrate and light reflected by a back side ofthe substrate. The above logic is made with the proviso that thesubstrate has a reflectivity of 1. In reality, many of the substrateshave reflectivities on the order of 1.5 so that a calculated value basedon the reflectivity of 1.5 is greater than the angle determined by theabove logic. However, the energy of the beam spot is attenuated atlongitudinal opposite ends and hence, the effect of interference at theopposite end portions is insignificant. Thus, the above logical valueprovides an adequate effect to attenuate interference.

This embodiment may be implemented in combination with Embodiment 1.

Embodiment 3

In this embodiment, description is made on an example where the size ofthe laser beam spots is changed by changing the length of the slit inthe course of laser irradiation using a plurality of laser oscillators.

The laser irradiation equipment provided at the semiconductorfabricating apparatus of the invention is arranged such that thecomputer determines an area to be scanned with the laser light based onthe mask information inputted to the computer. The embodiment is furtheradapted to change the length of the beam spot according to theconfiguration of the mask.

FIG. 26A shows an exemplary relation between a configuration of a maskused for patterning the semiconductor film and a length of the beam spotin a case where a single laser irradiation process is performed. Areference numeral 560 denotes a configuration of the mask used forpatterning the semiconductor film. After crystallization by the laserirradiation, the semiconductor film is patterned using the mask.

Reference numerals 561, 562 denote areas irradiated with the laserlight. The reference numerals 561, 562 denote the area scanned with abeam spot formed by synthesizing beam spots of laser beams outputtedfrom four laser oscillators. The reference numeral 562 is controlled bythe slit so as to have shorter length than that of the 561.

FIG. 26B shows an exemplary relation between a configuration of a maskused for patterning the semiconductor film and a length of the beam spotin a case where two laser irradiation processes are performed. Areference numeral 360 denotes a configuration of the mask used forpatterning the semiconductor film. After crystallization by the twolaser irradiation processes, the semiconductor film is patterned usingthe mask.

A reference numeral 363 denotes an area irradiated with a first laserlight. Although the first laser light is irradiated on the overallsurface of the semiconductor film according to this embodiment, thelaser light may be locally irradiated such that at least a portionforming an active layer after patterning may be crystallized. It iscritical that the portion forming the active layer after patterning isnot overlapped by an edge of the beam spot.

Reference numerals 361, 362 denote areas irradiated with the secondlaser light. The reference numerals 361, 362 denote the area scannedwith a beam spot formed by synthesizing beam spots of laser beamsoutputted from four laser oscillators. The reference numeral 362 iscontrolled by the slit so as to have shorter length than that of the361.

In an alternative approach, the first laser light may be locallyirradiated and the second laser light may be irradiated on the overallsurface of the semiconductor film.

In the case exemplified by the embodiment, since the slit is used, thelength of the beam spot is changed freely without stop the output of alllaser oscillation apparatus, so that it can prevent the output frombecoming unsteadily due to stop the output of the laser irradiationapparatus.

The above arrangement permits the path of the laser light to be changedin width and therefore, an edge of the laser light path is preventedfrom overlapping a semiconductor device obtained by patterning.Furthermore, the substrate may be further reduced in damage caused bythe laser light irradiated on an unwanted portion thereof.

The embodiment may be implemented in combination with any one ofEmbodiments 1 and 2.

Embodiment 4

In this embodiment, description is made on an example where the laserlight is selectively irradiated on a predetermined portion by operatingan AO modulator for blocking the laser light by changing the directionof the laser light in the course of laser irradiation performed by aplurality of laser oscillators. In this embodiment, the laser light isblocked by means of the AO modulator, it is not limited to this, anymeans may be used as long as the laser light is blocked.

The laser irradiation equipment of the invention is arranged such thatthe computer determines an area to be scanned with the laser light basedon the mask information inputted to the computer. The embodiment isfurther adapted to block the laser light by means of the AO modulator inorder that the laser light is selectively irradiated on the portion tobe scanned. In this case, the AO modulator may preferably be formed of amaterial capable of blocking the laser light and being less susceptibleto deformation or damage caused by the laser light.

FIG. 27A shows an exemplary relation between a configuration of a maskused for patterning the semiconductor film and an area to be irradiatedwith the laser light. A reference numeral 570 denotes a configuration ofthe mask used for patterning the semiconductor film. Aftercrystallization by the laser irradiation, the semiconductor film ispatterned using the mask.

A reference numeral 571 denotes a portion irradiated with the laserlight. A broken line denotes a portion where the laser light is blockedby the AO modulator. Thus, the embodiment is arranged such that theportion where crystallization is not required is not irradiated with thelaser light or irradiated with light of a reduced energy density.Accordingly, the substrate may be further reduced in damage caused bythe laser light irradiated on an unwanted portion thereof.

FIG. 27B shows an exemplary relation between a configuration of a maskused for patterning the semiconductor film and an area irradiated withthe laser light in a case where two laser irradiation processes areperformed. A reference numeral 370 denotes a configuration of the maskused for patterning the semiconductor film. After crystallization by thelaser irradiations, the semiconductor film is patterned using the mask.

A reference numeral 373 denotes an area irradiated with a first laserlight. Although the first laser light is irradiated on the overallsurface of the semiconductor film in this embodiment, the laser lightmay be locally applied such that at least a portion forming an activelayer after patterning may be crystallized. It is critical that theportion forming the active layer after patterning is not overlapped byan edge of the beam spot.

A reference numeral 371 denotes a portion irradiated with a second laserlight. A broken line denotes a portion where the laser light is blockedby the shutter. Thus, the embodiment is arranged such that the portionwhere crystallization is not required is not irradiated with the laserlight or irradiated with light of a reduced energy density. Accordingly,the substrate may be further reduced in damage caused by the laser lightirradiated on an unwanted portion thereof.

In an alternative approach, the first laser light may be locallyirradiated and the second laser light may be irradiated on the overallsurface of the semiconductor film.

Next, description is made on a process for fabricating a semiconductordisplay unit including a pixel portion, signal line drive circuit andscanning line drive circuit, the process wherein the AO modulator isused for selectively subjecting the pixel portion, the signal line drivecircuit and the scanning line drive circuit to a single laserirradiation process.

As shown in FIG. 28A, the laser light is scanned along a direction of anarrow in the figure thereby exposing the signal line drive circuit 302and the pixel portion 301 to the laser light. In this process, the laserlight is not irradiated on the overall surface of the substrate. Theshutter is used for blocking the laser light thereby obviating the lightirradiation on the scanning line drive circuit 303.

Next, as shown in FIG. 28B, the laser light is scanned along a directionof an arrow in the figure thereby exposing the scanning line drivecircuit 393 to the laser light. In this process, the signal line drivecircuit 392 and the pixel portion 391 are not exposed to the laserlight.

Next, referring to FIG. 29, description is made on another example wherethe shutter is used for selectively subjecting the pixel portion, thesignal line drive circuit and the scanning line drive circuit to asingle laser irradiation process.

As shown in FIG. 29A, the laser light is scanned along a direction of anarrow in the figure, thereby exposing a scanning line drive circuit 393and a pixel portion 391 to the laser light. In this Process, the laserlight is not irradiated on the overall surface of the substrate and theAO modulator is used for blocking the laser light thereby obviating thelight irradiation on a signal line drive circuit 392.

Next, as shown in FIG. 29B, the laser light is scanned along a directionof an arrow in the figure thereby exposing the signal line drive circuit392 to the laser light. In this process, the signal line drive circuit393 and the pixel portion 391 are not exposed to the laser light.

The AO modulator may be used in this manner for selectively irradiatingthe laser light so that the scanning direction of the laser light oneach circuit may be changed according to the layout of the channelforming regions of the active layers in each circuit. This preventsdouble laser irradiation on the same circuit, thus negating the need forrestrictions on the definition of the laser light path and on the layoutof the active layers in order to prevent the edge of the second laserlight from overlapping the laid out active layers.

Next, description is made on an example where a plurality of panels areformed from a large substrate and the AO modulator is used forselectively subjecting the pixel portion, the signal line drive circuitand the scanning line drive circuit to a single laser irradiationprocess.

First, as shown in FIG. 30, the laser light is scanned along a directionof an arrow in the figure thereby exposing a signal line drive circuit382 and a pixel portion 381 of each panel to the laser light. In thisprocess, the laser light is not irradiated on the overall surface of thesubstrate and the shutter is used for blocking the laser light therebyobviating the light irradiation on a scanning line drive circuit 383.

Next, the laser light is scanned along a direction of an arrow in thefigure, thereby exposing the scanning line drive circuit 383 to thelaser light. In this process, the signal line drive circuit 382 and thepixel portion 381 are not exposed to the laser light. Incidentally, areference numeral 385 denotes a scribe line on a substrate 386.

This embodiment may be implemented in combination with any one ofEmbodiments 1 to 3.

Embodiment 5

In this embodiment, there will be described an example of a markerprovided on a marker forming portion 463.

FIG. 31A shows the top view of markers of this embodiment. Referencenumerals 461 and 462 denote markers (hereinafter referred to as thereference markers) that will function as reference points formed in asemiconductor film, with each of the reference markers having arectangular shape. All of the reference markers 461 are disposed so thatlong sides of the rectangles extend in the horizontal direction, withrespective reference markers 461 being disposed in the verticaldirection at regular intervals. All of the reference markers 462 aredisposed so that long sides of the rectangles extend in the verticaldirection, with respective reference markers 462 being disposed in thehorizontal direction at regular intervals.

The reference markers 461 become reference points with reference towhich there are determined the positions of the masks in the verticaldirection, while the reference markers 462 become reference points withreference to which there are determined the positions of the masks inthe horizontal direction. Reference numerals 464 and 465 denote markersfor the masks for patterning the semiconductor film, with each of themarkers having a rectangular shape. The positions of the masks for thesemiconductor patterning are determined so that the long sides of therectangular marker 464 are disposed in the horizontal direction and thelong sides of the rectangular marker 465 are disposed in the verticaldirection. In addition, the positions of the masks for the semiconductorpatterning are determined so that the masks are precisely positioned atthe center between two adjacent reference markers 461 that determine themarkers 464 and are also precisely positioned at the center between twoadjacent reference markers 462 that determine the markers 465.

FIG. 31B is a perspective view of the reference markers formed in thesemiconductor film. Parts of the semiconductor film 470 formed on thesubstrate 471 are cut away by a laser in a rectangular shape and thecut-away portions function as the reference markers 461 and 462.

It should be noted here that the markers described in this embodimentare just an example and the markers of the present invention are notlimited to these markers. There occurs no problem so long as it ispossible to form the markers of the present invention prior to thecrystallization of the semiconductor film with the laser beams and alsoto use the markers even after the crystallization by the irradiation ofthe laser beams.

Next, an example is made on the structure of the optical system forforming marker included in the laser irradiation equipment of thepresent invention with reference to FIG. 32. In FIG. 32, referencenumeral 350 is a reticule for forming the patterning of the marker. Thelaser beam through the reticule 350 is condensed at a convex lens 351,and irradiated to a semiconductor film 353 formed on a substrate 352. Aportion of the semiconductor film where the laser beam is irradiated isremoved, and an opening potion 354 is formed. The opening portion may beused as a marker.

The optical system for projecting the reticule pattern by reducing isnot limited to the convex lens 351. Any can be used as long as it canreduce the reticule pattern. If the reticule pattern can be formed sameorder as that of the marker, the optical system for projecting thereticule pattern by reducing is not necessary.

Reference to FIG. 32, the lens 351 has two principle points. Distance ofthe principle point A closest to the reticule 350 and the reticule 350is defined to be L₁, on the other hand, distance of the principle pointB closest to the semiconductor film 353 and the semiconductor film 353is defined to be L₂. Therefore, the formula for the focal length f ofthe lens 351 is the formula 1 as follows. As in the case that twoprinciple points are identical, L₁ and L₂ can be defined.1/f=1/L ₁+1/L ₂  [Formula 1]

The formula for a pace of expansion is the formula 2 as follows.M=L ₂ /L ₁  [Formula 2]

If the focal length f of the lens 351 is determined by using the formula1 and formula 2, the pace of expansion M is determined.

It is possible to implement this embodiment in combination withEmbodiments 1 to 4.

Embodiment 6

In this embodiment, a method of manufacturing an active matrix substratewhen the semiconductor film is crystallized in the case that a laserbeam is irradiated two times will be described with reference to FIGS.33 to 36. A substrate on which a CMOS circuit, a driver circuit, and apixel portion having a pixel TFT and a retention capacity are formedtogether is referred to as an active matrix substrate for convenience.

First of all, a substrate 600 formed of glass such as bariumborosilicate glass and aluminum borosilicate glass is used in thisembodiment. The substrate 600 may be a quartz substrate, a siliconsubstrate, a metal substrate or stainless substrate, which has aninsulating film on the surface. The substrate 600 may be a plasticsubstrate having heat resistance, which withstands a processingtemperature in this embodiment.

Next, a base film 601 comprising of a silicon oxide film, a siliconnitride film, or a silicon oxynitride film is formed on the base film601 by publicly known method (such as the sputtering method, LPCVDmethod and plasma CVD method). In this embodiment, as a base film 601,two-layer base film 601 a and 601 b are used, however, a single layer ofthe insulating film or two or more laminated layers may also be used(FIG. 33A).

Next, an amorphous semiconductor film 692 is formed on the base film 601by publicly known method (such as the sputtering method, LPCVD methodand plasma CVD method) to have a thickness of 25 to 80 nm (preferably,30 to 60 nm) (FIG. 33B). In this embodiment, an amorphous semiconductorfilm is formed. However, micro-crystalline semiconductor film andcrystalline semiconductor film may be formed. In addition, a compoundsemiconductor film having an amorphous structure such as an amorphoussilicon germanium film may be used.

The amorphous semiconductor film 692 is crystallized by using the lasercrystallization. The laser crystallization is conducted by using thelaser irradiation method of the present invention. In the presentinvention, the amorphous semiconductor film is irradiated the laser beamtwo times according to a mask information inputted into the computer ofthe laser apparatus. Of course, the crystallization may be conducted byusing not only the laser crystallization, but also being combined withanother known crystallization method (thermal crystallization methodusing RTA and an annealing furnace or using metal elements promotingcrystallization).

When a crystallization of an amorphous semiconductor film is conducted,it is preferable that the second harmonic through the fourth harmonic ofbasic waves is applied by using the solid state laser which is capableof continuous oscillation in order to obtain a crystal in large grainsize. Typically, it is preferable that the second harmonic (with awavelength of 532 nm) or the third harmonic (with a wavelength of 355nm) of an Nd YVO₄ laser (basic wave of 1064 nm) is applied.Specifically, laser beams emitted from the continuous oscillation typeYVO₄ laser with 10 W output is converted into a harmonic by using thenon-linear optical elements. Also, a method of emitting a harmonic byapplying crystal of YVO₄ and the non-linear optical elements into aresonator. Then, more preferably, the laser beams are formed so as tohave a rectangular shape or an elliptical shape by an optical system,thereby irradiating a substance to be treated. At this time, the energydensity of approximately 0.01 to 100 MW/cm²(preferably 0.1 to 10 MW/cm²)is required. The semiconductor film is moved at approximately 10 to 2000cm/s rate relatively corresponding to the laser beams so as to irradiatethe semiconductor film.

Note that, for a two times laser irradiation, a gas laser or solid-statelaser of continuous oscillation type or pulse oscillation type can beused. The gas laser such as an excimer laser, Ar laser, Kr laser and thesolid-state laser such as YAG laser, YVO₄ laser, YLF laser, YalO₃ laser,glass laser, ruby laser, alexandrite laser, Ti: sapphire laser, Y₂O₃laser can be used as the laser beam. Also, crystals such as YAG laser,YVO₄ laser, YLF laser, YAlO₃ laser wherein Cr, Nd, Er, Ho, Ce, Co, Ti,Yb or Tm is doped can be used as the solid-state laser. A basic wave ofthe lasers is different depending on the materials of doping, thereforea laser beam having a basic wave of approximately 1 μm is obtained. Aharmonic corresponding to the basic wave can be obtained by the usingnon-linear optical elements.

By the above-mentioned laser crystallization, the regions 693, 694, and695 are formed that is increased the crystallinity by two times laserirradiation with respect to the amorphous semiconductor film (FIG. 33B).

The island like semiconductor films 602 to 606 are formed from thecrystallized regions 693, 694, and 695 by performing patterningprocessing the crystallized semiconductor film into desired shape thatis increased the crystallinity in part (FIG. 33C).

After the island like semiconductor films 602 to 606 are formed, a smallamount of impurity element (boron or phosphorus) may be doped in orderto control a threshold value of the TFT.

Next, a gate insulating film 607 covering the island like semiconductorfilms 602 to 606 is formed. The gate insulating film 607 is formed byusing an insulating film containing silicon with a thickness of 40 to150 nm by using plasma CVD method or sputtering method. In thisembodiment, a silicon oxynitride film (compositional ratio: Si=32%,O=59%, N=7% and H=2%) with a thickness of 110 nm is formed by the plasmaCVD method. Notably, the gate insulating film is not limited to thesilicon oxynitride film but an insulating film containing other siliconmay be used as a single layer or as a laminated pad.

When a silicon oxide film is used, it is formed by mixing TetraethylOrthosilicate (IEOS) and O₂ by plasma CVD method, which is dischargedunder a condition with reaction pressure of 40 Pa, a substratetemperature of 300 to 400° C. and high frequency (13.56 MHz) powerdensity of 0.5 to 0.8 W/cm². Thermal annealing at 400 to 500° C.thereafter can give good characteristics to the silicon oxide filmproduced in this way as a gate insulating film.

Next, a first conductive film 608, which is 20 to 100 nm in thickness,and a second conductive film 609, which is 100 to 400 nm in thickness,is stacked on the gate insulating film 607. In this embodiment, thefirst conductive film 608 formed by a TaN film with a thickness of 30 nmand the second conductive film 609 formed by a W film with a thicknessof 370 nm are stacked. The TaN film is formed by using Ta target toperform sputtering in an atmosphere containing nitrogen. The W film isformed by using W target to perform sputtering. Alternatively, it can beformed by thermal CVD method using tungsten hexafluoride (WF₆). In bothcases, the use of the gate electrode needs low resistance. Therefore,the resistivity of the W film is desirably 20 μΩcm or less. The lowresistance of the W film can be achieved by increasing the size of thecrystal grains. However, when the W film contains a large amount ofimpurity element such as oxygen, the crystallization is inhibited, whichraises the resistance. Accordingly, in this embodiment, the W film isformed by the sputtering method using high purity (purity of 99.9999%) Wtarget and by taking the prevention of intrusion of impurity from avapor phase during the film forming into special consideration. Thus,the resistivity of 9 to 20 μΩcm can be achieved.

While, in this embodiment, the first conductive film 608 is TaN and thesecond conductive film 609 is W, they are not limited in particular.Both of them can be formed by an element selected from Ta, W, Ti, Mo,Al, Cu, Cr and Nd or an alloy material or a compound material mainlycontaining the element. Alternatively, a semiconductor film, such as apolycrystalline silicon film to which an impurity element such asphosphorus is doped, can be used. An AgPdCu alloy may be used. Acombination of the first conductive film formed by a tantalum (Ta) filmand the second conductive film formed by a W film, a combination of thefirst conductive film formed by a titan nitride (TiN) film and thesecond conductive film formed by a W film, a combination of the firstconductive film formed by a tantalum nitride (TaN) film and the secondconductive film formed by a W film, a combination of the firstconductive film formed by a tantalum nitride (TaN) film and the secondconductive film formed by an Al film, or a combination of the firstconductive film formed by a tantalum nitride (TaN) film and the secondconductive film formed by a Cu film is possible.

Further, the present invention is not limited to a two-layer structure.For example, a three-layer structure may be adopted in which a tungstenfilm, an alloy film of aluminum and silicon (Al—Si), and a titaniumnitride film are sequentially laminated. Moreover, in case of athree-layer structure, tungsten nitride may be used in place oftungsten, an alloy film of aluminum and titanium (Al—Ti) may be used inplace of the alloy film of aluminum and silicon (Al—Si), and a titaniumfilm may be used in place of the titanium nitride film.

Note that, it is important that appropriate etching method or kinds ofetchant is properly selected depending on the materials of a conductivefilm.

Next, masks 610 to 615 made of resist using photolithography method areformed, and first etching processing is performed thereon in order toform electrodes and wires. The first etching processing is performedunder first and second etching conditions (FIG. 34B). The first etchingcondition in this embodiment is to use Inductively Coupled Plasma (ICP)etching and to use CF₄ and Cl₂ and O₂ as an etching gas, whose amount ofgases are 25/25/10 (sccm), respectively. 500 W of RF (13.56 MHz) powerwas supplied to a coil type electrode by 1 Pa pressure in order togenerate plasma and then to perform etching. 150 W of RF (13.56 MHz)power was also supplied to a substrate side (test sample stage) andsubstantially negative self-bias voltage was applied. The W film wasetched under the first etching condition so as to obtain the end of thefirst conductive layer in a tapered form.

After that, the first etching condition is shifted to the second etchingcondition without removing the masks 610 to 615 made of resist. Then,CF₄ and Cl₂ are used as etching gases. The ratio of the amounts offlowing gasses is 30/30 (sccm). 500 W of RF (13.56 MHz) power issupplied to a coil type electrode by 1 Pa pressure in order to generateplasma and then to perform etching for amount 30 seconds. 20 W of RF(1356 MHz) power is also supplied to a substrate side (test samplestage) and substantially negative self-bias voltage is applied. Underthe second etching condition where CF₄ and Cl₂ are mixed, both W filmand TaN film were etched to the same degree. In order to etch withoutleaving a residue on the gate insulating film, the etching time may beincreased 10 to 20% more.

In the first etching processing, when the shape of the mask made ofresist is appropriate, the shape of the ends of the first and the secondconductive layers are in the tapered form due to the effect of the biasvoltage applied to the substrate side. The angle of the tapered portionis 15 to 45°. Thus, conductive layers 617 to 622 in a first form areformed which include the first conductive layers and the secondconductive layers (first conductive layers 617 a to 622 a and secondconductive layer 617 b to 622 b) through the first etching processing.In a gate insulating film 616, an area not covered by the conductivelayers 617 to 622 in the first form is etched by about 20 to 50 nm so asto form a thinner area.

Next, second etching processing is performed without removing masks madeof resist (FIG. 34C). Here, CF₄, Cl₂ and O₂ are used as an etching gasto etch the W film selectively. Then, second conductive layers 628 b to633 b are formed by the second etching processing. On the other hand,the first conductive layers 617 a to 622 a are hardly etched, andconductive layers 628 to 633 in the second form are formed.

First doping processing is performed without removing masks made ofresist and low density of impurity element, which gives n-type to thesemiconductor film, is added. The doping processing may be performed bythe ion-doping method or the ion-implanting method. The ion dopingmethod is performed under a condition in the dose of 1×10¹³ to 5×10¹⁴atoms/cm² and the accelerating voltage of 40 to 80 kV. In thisembodiment, the ion doping method is performed under a condition in thedose of 1.5×10¹³ atoms/cm² and the accelerating voltage of 60 kV. Then-type doping impurity element may be Group 15 elements, typicallyphosphorus (P) or arsenic (As). Here, phosphorus (P) is used. In thiscase, the conductive layers 628 to 633 function as masks for the n-typedoping impurity element. Therefore, impurity areas 623 to 627 are formedin the self-alignment manner. An n-type doping impurity element in thedensity range of 1×10¹⁸ to 1×10²⁰ atoms/cm³ are added to the impurityareas 623 to 627.

When masks made of resist are removed, new masks 634 a to 634 c made ofresist are formed. Then, second doping processing is performed by usinghigher accelerating voltage than that used in the first dopingprocessing. The ion doping method is performed under a condition in thedose of 1×10¹³ to 1×10¹⁵ atoms/cm² and the accelerating voltage of 60 to120 kV. In the doping processing, the second conductive layers 628 b to632 b are used as masks against the impurity element. Doping isperformed such that the impurity element can be added to thesemiconductor film at the bottom of the tapered portion of the firstconductive layer. Then, third doping processing is performed by havinglower accelerating voltage than that in the second doping processing toobtain a condition shown in FIG. 35A. The ion doping method is performedunder a condition in the dose of 1×10¹⁵ to 1×10¹⁷ atoms/cm² and theaccelerating voltage of 50 to 100 kV. Through the second dopingprocessing and the third doping processing, an n-type doping impurityelement in the density range of 1×10¹⁸ to 5×10¹⁹ atoms/cm³ is added tothe low density impurity areas 636, 642 and 648, which overlap with thefirst conductive layer. An n-type doping impurity element in the densityrange of 1×10¹⁹ to 5×10²¹ atoms/cm³ is added to the high densityimpurity areas 635, 641, 644 and 647.

With proper accelerating voltage, the low density impurity area and thehigh density impurity area can be formed by performing the second dopingprocessing and the third doping processing once.

Next, after removing masks made of resist, new masks 650 a to 650 c madeof resist are formed to perform the fourth doping processing. Throughthe fourth doping processing, impurity areas 653, 654, 659 and 660, towhich an impurity element doping a conductive type opposite to the oneconductive type is added, in a semiconductor layer, which is an activelayer of a p-channel type TFT. Second conductive layers 628 a to 632 aare used as mask against the impurity element, and the impurity elementgiving p-type is added so as to form impurity areas in theself-alignment manner. In this embodiment, the impurity areas 653, 654,659 and 660 are formed by applying ion-doping method using diborane(B₂H₆) (FIG. 35B). During the fourth doping processing, thesemiconductor layer forming the n-channel TFT is covered by masks 650 ato 650 c made of resist. Thorough the first to the third dopingprocessing, phosphorus of different densities is added to each of theimpurity areas 653, 654, 659 and 660. Doping processing is performedsuch that the density of p-type doping impurity element can be 1×10¹⁹ to5×10²¹ atoms/cm³ in both areas. Thus, no problems are caused when theyfunction as the source region and the drain region of the p-channel TFT.

Impurity areas are formed in the island like semiconductor layers,respectively, through the processes above.

Next, the masks 650 a to 650 c made of resist are removed and a firstinterlayer insulating film 661 is formed thereon. The first interlayerinsulating film 661 may be an insulating film with a thickness of 100 to200 nm containing silicon, which is formed by plasma CVD method orsputtering method. In this embodiment, silicon oxynitride film with athickness of 150 nm is formed by plasma CVD method. The first interlayerinsulating film 661 is not limited to the silicon oxynitride film butmay be the other insulating film containing silicon in a single layer orin a laminated pad.

Next, as shown in FIG. 35C, activation processing is performed by usinglaser irradiation method. When a laser annealing method is used, thelaser used in the crystallization can be used. When the activationprocessing is performed, the moving speed is same as thecrystallization, and an energy density of about 0.01 to 100 MW/cm²(preferably, 0.01 to 100 MW/cm²) is required. Also, a continuousoscillation laser may be used in the case the crystallization isperformed and a pulse oscillation laser may be used in the case theactivation is performed.

Also, the activation processing may be conducted before the firstinterlayer insulating film is formed.

After the heating processing (thermal processing at 300 to 550° C. for 1to 12 hours) is performed, hydrogenation can be performed. This processterminates the dangling bond of the semiconductor layer with hydrogencontained in the first interlayer insulating film 661. Alternatively,the hydrogenation may be plasma hydrogenation (using hydrogen excited byplasma) or heating processing in an atmosphere containing 3 to 100% ofhydrogen at 300 to 650° C. for 1 to 12 hours. In this case, thesemiconductor film may be hydrogenated irrespective of an existence ofthe first interlayer insulating film.

Next, a second interlayer insulating film 662 formed by an inorganicinsulating material or an organic insulator material is formed on thefirst interlayer insulating film 661. In this embodiment, an acrylicresin film us formed to have a thickness of 1.6 μm. Subsequently, thethird interlayer insulating film 672 is formed to contact with thesecond interlayer insulating film 662 after the second interlayerinsulating film is formed.

Wirings 664 to 668 electrically connecting to impurity areas,respectively, are formed in a driver circuit 686. These wirings areformed by patterning a film laminating a Ti film with a thickness of 50nm and an alloy film (alloy film of Al and Ti) with a thickness of 500nm. It is not limited to the two-layer structure but may be a one-layerstructure or a laminate pad including three or more layers. Thematerials of the wirings are not limited to Al and Ti. For example, thewiring can be formed by forming Al or Cu on a TaN film and then bypatterning the laminate film in which a Ti film is formed (FIG. 36).

In a pixel portion 687, a pixel electrode 670, a gate wiring 669 and aconnecting electrode 668 are formed. Source wirings (a laminate oflayers 643 a and 643 b) are electrically connected with a pixel TFT bythe connecting electrode 668. The gate wiring 669 is electricallyconnected with a gate electrode of the TFT pixel 684. A pixel electrode670 is electrically connected with a drain region 690 of the pixel TFT.Furthermore, the pixel electrode 670 is electrically connected with anisland-like semiconductor film 685 functioning as one electrode forminga storage capacitor. In the present invention, the pixel electrode andthe connection electrode are made from same materials, however, amaterial having excellent reflectivity such as a film mainly containingAl or Ag or the laminate film is used for the pixel electrode 670.

In this way, the driver circuit 686 having a CMOS circuit including ann-channel TFT 681 and a p-channel TFT 682 and a n-channel TFT 683, andthe pixel portion 687 having the pixel TFT 684 and the retentioncapacitor 685 can be formed on the same substrate. Thus, an activematrix substrate is completed.

The n-channel TFT 681 of the driver circuit 686 has a channel formingregion 637, a low density impurity area 636 overlapping with the firstconductive layer 628 a, which constructs a part of the gate electrode(GOLD (Gate Overlapped LDD) area), and a high density impurity area 652functioning as the source region or the drain region are implanted. Thep-type channel TFT 682 forming a CMOS circuit together with then-channel TFT 681, which are connected by an electrode 666, has achannel forming region 640, a high density impurity area 653 functioningas the source region or the drain region, and an impurity area 654 towhich a p-type doping impurity element are implanted. The n-channel TFT683 has a channel forming region 643, a low density impurity area 642overlapping with the first conductive layer 630 a, which constructs apart of the gate electrode, (GOLD area), and a high density impurityarea 656 functioning as the source region or the drain region.

The pixel TFT 684 of the pixel portion has a channel forming region 646,a low density impurity area 645 formed outside of the gate electrode(LDD region) and a high density impurity area 658 functioning as thesource region or the drain region. An n-type doping impurity element anda p-type doping impurity element are added to a semiconductor layerfunctioning as one electrode of the storage capacitor 685. The storagecapacitor 685 is formed by an electrode (a laminate of layers 632 a and632 b) and a semiconductor layer by using the insulating film 616 as adielectric.

The pixel structure in this embodiment is arranged such that light canbe blocked in a space between pixel electrodes and the ends of the pixelelectrodes can overlap with the source wiring without using the blackmatrix.

This embodiment can be implemented by combining with Embodiments 1 to 5.

Embodiment 7

This embodiment explains, below, a process to manufacture a reflectiontype liquid crystal display device from the active matrix substrate madein Embodiment 6, using FIG. 37.

First, after obtaining an active matrix substrate in the state of FIG.36 according to Embodiment 6, an alignment film 867 is formed at leaston the pixel electrodes 670 on the active matrix substrate of FIG. 36and subjected to a rubbing process. Incidentally, in this embodiment,prior to forming an alignment film 867, an organic resin film such as anacryl resin film is patterned to form columnar spacers 872 in a desiredposition to support the substrates with spacing. Meanwhile, sphericalspacers, in place of the columnar spacers, may be distributed over theentire surface of the substrate.

Then, a counter substrate 869 is prepared. Then, coloring layers 870,871 and a planarizing film 873 are formed on a counter substrate 869. Ashade portion is formed by overlapping a red coloring layer 870 and ablue coloring layer 871 together. Meanwhile, the shade portion may beformed by partly overlapping a red coloring layer and a green coloringlayer.

In this embodiment is used a substrate shown in Embodiment 6. There is aneed to shade at least the gap between the gate wiring 669 and the pixelelectrode 670, the gap between the gate wiring 669 and the connectingelectrode 668, and the gap between the connecting electrode 668 and thepixel electrode 670. In this embodiment were bonded together thesubstrates by arranging the coloring layers so that the shieldingportion having a lamination of coloring layers is overlapped with theto-be-shielding portion.

In this manner, the gaps between the pixels are shaded by the shieldingportion having a lamination of coloring layers without forming ashielding layer such as a black mask, thereby enabling to reduce thenumber of processes.

Then, a counter electrode 876 of a transparent conductive film is formedon the planarizing film 873 at least in the pixel portion. An alignmentfilm 874 is formed over the entire surface of the counter substrate andsubjected to a rubbing process.

Then, the active matrix substrate formed with the pixel portion anddriver circuit and the counter substrate are bonded together by a sealmember 868. The seal member 868 is mixed with filler so that the fillerand the columnar spacers bond together the two substrates through aneven spacing. Thereafter, a liquid crystal material 875 is pouredbetween the substrates, and completely sealed by a sealant (not shown).The liquid crystal material 875 may be a known liquid crystal material.In this manner, completed is a reflection type liquid crystal displaydevice shown in FIG. 37. If necessary, the active matrix substrate orcounter substrate is divided into a desired shape. Furthermore, apolarizing plate (not shown) is bonded only on the counter substrate.Then, an FPC is bonded by a known technique.

The liquid crystal display device manufactured as above comprises TFTmanufactured by a semiconductor film, wherein a laser beam having aperiodic or uniform energy distribution is irradiated and a crystalgrain with a large grain size is formed. Thus, the liquid crystaldisplay device ensures a good operational characteristic and highreliability. The liquid crystal display device can be used as a displayportion for an electronic appliance in various kinds.

Incidentally, this embodiment can be implemented by combining withEmbodiments 1 to 6.

Embodiment 8

This embodiment explains an example of manufacturing a light emittingdevice by using a method of manufacturing TFT when an active matrixsubstrate is fabricated in the Embodiment 6. In this specification, thelight-emitting device refers, generally, to the display panel havinglight-emitting elements formed on a substrate sealed between thesubstrate and a cover member, and the display module having TFTs or thelike mounted on the display panel. Incidentally, the light emittingelement has a layer including an organic compound thatelectroluminescence caused is obtained by applying an electric field(light emitting layer), an anode layer and a cathode layer. Meanwhile,the electroluminescence in compound includes the light emission uponreturning from the singlet-excited state to the ground state(fluorescent light) and the light emission upon returning from thetriplet-excited state to the ground state (phosphorous light), includingany or both of light emission.

Note that, all the layers that are provided between an anode and acathode in a light emitting element are defined as an organic lightemitting layer in this specification. Specifically, the organic lightemitting layer includes a light emitting layer, a hole injection layer,an electron injection layer, a hole transporting layer, an electrontransporting layer, etc. A basic structure of a light emitting elementis a laminate of an anode layer, a light emitting layer, and a cathodelayer layered in this order. The basic structure can be modified into alaminate of an anode layer, a hole injection layer, a light emittinglayer, and a cathode layer layered in this order, or a laminate of ananode layer, a hole injection layer, a light emitting layer, an electrontransporting layer, and a cathode layered in this order.

The light emitting element used in this embodiment comprising the holeinjection layer, the electron injection layer, the hole transportinglayer, and the electron transporting layer may be solely formed byinorganic compounds, or materials mixed with organic compounds andinorganic compounds. The light emitting element may be formed by mixtureof these layers.

FIG. 38A is a sectional view of a light-emitting device of thisembodiment manufactured up through the third interlayer insulating film750. In FIG. 38A, the switching TFT 733 and the current controlling TFT734 provided on the substrate 700 is formed by using the manufacturingmethod in Embodiment 6. Incidentally, although this embodiment is of adouble gate structure formed with two channel forming regions, it ispossible to use a single gate structure formed with one channel formingregion or a triple gate structure formed with three channel formingregions. In this embodiment, the current controlling TFT 734 has asingle gate structure in which one channel formation region is formed,however the current controlling TFT may also have a structure in whichtwo channel formation region are formed.

The n-channel TFT 731 and the p-channel TFT 732 in the driver circuitprovided on the substrate 700 is formed by using the manufacturingmethod in Embodiment 6. Incidentally, although this embodiment is of asingle gate structure, it is possible to use a double gate structure ora triple gate structure.

In the case of the light-emitting device, the third interlayerinsulating film 750 is effective to prevent water contained in thesecond interlayer insulating film 751 from penetrating into the organiclight emitting layer. If the second interlayer insulating film 751 hasorganic resin material, providing the third interlayer insulating film750 is effective because the organic resin materials contain water alot.

Completed the manufacture process up through the step of forming thethird interlayer insulating film in Embodiment 6, the pixel electrode711 is formed on the third interlayer insulating film 750.

Meanwhile, reference numeral 711 is a pixel electrode (anode of alight-emitting element) formed by a transparent conductive film. As thetransparent conductive film can be used a compound of indium oxide andtin oxide, a compound of indium oxide and zinc oxide, zinc oxide, tinoxide or indium oxide. A transparent conductive film added with galliummay also be used. The pixel electrode 711 is formed on a planar thirdinterlayer insulating film 750 prior to forming the wirings. In thisembodiment, it is very important, to planarize the step due to the TFTby using a the second interlayer insulating film 751 made of resin. Alight emitting layer to be formed later, because being extremely thin,possibly causes poor light emission due to the presence of a step.Accordingly, it is desired to provide planarization prior to forming apixel electrode so that a light emitting layer can be formed as planaras possible.

Next, as shown in FIG. 38B, the resin film which distributed black dye,carbon, or black pigment is deposited, so that the third layerinsulating film 750 may be covered, and the shielding film 770 isdeposited by forming a opening portion in the portion which serves as alight emitting element. In addition, as materials for resin, althoughpolyimide, polyamide, acrylics, BCB (benzocyclobutene), and the like arementioned typically, it is not limited to the above-mentioned material.Moreover, it is also possible to use materials that is mixed black dye,carbon, or black pigments with silicon, silicon oxide, siliconoxynitride, and the like as a material of a cover film other thanorganic resin. The shielding film 770 is effective in the external lightreflected in wires 701 to 707 preventing going into an observer's eyes.

After the pixel electrode 711 is formed, contact holes are formed in thegate insulating film 752, the first interlayer insulating film 753, thesecond interlayer insulating film 751, the third interlayer insulatingfilm 750, the shielding film 770 respectively. The conductive film isformed to overlap the pixel electrode 711 on the shielding film 770.Wirings 701 to 707 are formed connected electrically to each impurityregion of TFT by etching the conductive film. Note that a laminationfilm of a 50 nm thick Ti film and a 500 nm thick alloy film (Al and Tialloy film) is patterned in order to form the wirings. There are nolimitations regarding the two layer structure, of course, and a singlelayer structure or a laminate structure having three or more layers mayalso be used. Further, the wiring material is not limited to Al and Ti.For example, a lamination film, in which Al or Cu is formed on a TaNfilm, and then a Ti film is formed, may be patterned, forming thewirings (FIG. 38A).

The wiring 707 is a source wiring (corresponding to the current supplyline) of the current controlling TFT 734. Reference numeral 706 is anelectrode that connects electrically the drain region of the currentcontrolling TFT 734 with the pixel electrode 711.

After forming wires 701 to 707, the bank 712 is formed that is made fromresin materials. The bank 712 is formed to expose a portion of the pixelelectrode 711 by patterning the acrylic film having 1 to 2 μm inthickness or polyimide film.

A light emitting layer 713 is formed on the pixel electrode 711.Incidentally, although FIG. 38B shows only one pixel, this embodimentseparately forms light emitting layers correspondingly to the respectivecolors of R (red), G (green) and B (blue). Meanwhile, in this embodimentis formed a low molecular weight organic light-emitting material by thedeposition method. Specifically, this is a lamination structure having acopper phthalocyanine (CuPc) film provided with a thickness of 20 nm asa hole injecting layer and a tris-8-qyuinolinolato aluminum complex(Alq₃) film provided thereon with a thickness of 70 nm as a lightemitting layer. The color of emission light can be controlled by addinga fluorescent pigment, such as quinacridone, perylene or DCM1, to Alq₃.

However, the foregoing example is an example of organic light-emittingmaterial to be used for a light emitting layer and not necessarilylimited to this. It is satisfactory to form a light emitting layer(layer for light emission and carrier movement therefore) by freelycombining a light emitting layer, a charge transporting layer and acharge injection layer. For example, although in this embodiment wasshown the example in which a low molecular weight organic light-emittingmaterial is used for a light emitting layer, it is possible to use anintermediate molecular weight organic light-emitting material or highmolecular weight organic light-emitting material. In this specification,an intermediate molecular weight organic light-emitting material isdefined that an aggregate of an organic compound which does not havesubliming property or dissolving property (preferably, an aggregatewhich has molecularity of 10 or less), or an organic compound which hasa molecular chain length of 5 μm of less (preferably 50 nm or less). Asan example of using high molecular electroluminescent emitting material,the laminated pad can be made polythiophene (PEDOT) films with athickness of 20 nm is provided by spin coating method as a holeinjection layer, and paraphenylene-vinylene (PPV) films with a thicknessof 100 nm is provided thereon as a light emitting layer. The lightemitting wave length can be selected from red through blue by usingπ-conjugated system high molecular of PPV. The inorganic material suchas a silicon carbide can be used as a charge transporting layer and acharge injection layer. These organic light-emitting material andinorganic light-emitting material are formed by using known materials.

Next, a cathode 714 of a conductive film is provided on the lightemitting layer 713. In this embodiment, as the conductive film is usedan alloy film of aluminum and lithium. A known MgAg film (alloy film ofmagnesium and silver) may be used. As the cathode material may be used aconductive film of an element belonging to the periodic-table group 1 or2, or a conductive film added with such an element.

A light-emitting element 715 is completed at a time having formed up tothe cathode 714. Incidentally, the light-emitting element 715 hereinrefers to a diode formed with a pixel electrode (anode) 711, a lightemitting layer 713 and a cathode 714.

It is effective to provide a protective film 754 in such a manner tocompletely cover the light-emitting element 715. The protective film 754is formed by an insulating film including a carbon film, a siliconnitride film or a silicon oxynitride film, and used is an insulatingfilm in a single layer or a combined lamination.

In such a case, it is preferred to use a film favorable in coverage as aprotective film 754. It is effective to use a carbon film, particularlyDLC (diamond-like carbon) film The DLC film, capable of being depositedin a temperature range of from room temperature to 100° C. or less, canbe easily deposited over the light emitting layer 713 low in heatresistance. Meanwhile, the DLC film, having a high blocking effect tooxygen, can suppress the light emitting layer 713 from oxidizing.Consequently, prevented is the problem of oxidation in the lightemitting layer 713 during the following seal process.

In this embodiment, the light emitting layer 713 is overlappedcompletely with a inorganic insulating film having high barrier propertysuch as a carbon film, a silicon nitride, a silicon oxynitride, aluminumnitride, or aluminum oxynitride, so that it can prevent effectively thedeterioration of the light emitting layer due to water and oxygen frompenetrating thereof into the light emitting layer.

Furthermore, it is preferable to use the silicon nitride film formed bysputtering method using silicon as a target for the third interlayerinsulating film 750, the passivation film 712, the protective film 754that the penetration of impurities into the light emitting layer isprevented effectively. The deposition condition may be appropriatelyselected, preferably, nitride (N₂) or a mixed gas of nitride and argonare used for sputtering gas, and sputtering is performed by applying ahigh frequency electric. The substrate temperature may be set as roomtemperature, and heating means are unnecessary to be used. If theorganic insulating film and the organic compound layer are formedalready, it is preferable that the deposition is conducted withoutheating the substrate. However, to remove completely absorbed water oroccluded water, it is preferable to perform dehydration by heating forseveral minutes to hours in vacuum at about 50 to 100° C.

The silicon nitride film formed by sputtering method at the condition:at room temperature using silicon as a target; applying 13.56 MHz highfrequency electric; and using nitride gas is characterized in that notonly the absorption peak of N—H association and Si—H association are notobserved but also the absorption peak of Si—O in the infrared absorptionspectrum. The oxide density and the hydrogen density is not more than 1atomic %. Thus, it can prevent more effectively impurities such asoxygen and water more effectively from penetrating into the lightemitting layer.

Furthermore, a seal member 717 is provided to overlap the light emittinglayer 715 to bond a cover member 718. For the seal member 717 used maybe an ultraviolet curable resin. It is effective to provide therein asubstance having a hygroscopic effect or an antioxidant effect.Meanwhile, in this embodiment, for the cover member 718 used is a glasssubstrate, quartz substrate or plastic substrate (including a plasticfilm) having carbon films (preferably diamond-like carbon films) formedon the both surfaces thereof.

Thus, completed is a light-emitting device having a structure as shownin FIG. 38B. Incidentally, it is effective to continuously carry out,without release to the air, the process to form a protective film afterforming a passivation film 712 by using a deposition apparatus of amulti-chamber scheme (or in-line scheme). In addition, with furtherdevelopment it is possible to continuously carry out the process up tobonding a cover member 718, without release to the air.

In this manner, n-channel TFTs 731, 732, a switching TFT (n-channel TFT)703 and a current control TFT (p-channel TFT) 734 are formed on thesubstrate 700.

The shielding film 770 is formed between the third interlayer insulatingfilm 750 and the bank 712 in this embodiment, however the presentinvention is not limited thereto. It is noted that the shielding film770 is provided at the position that enables the shielding film 770 toprevent the external light reflected in wires 701 to 707 preventinggoing into an observer's eyes. For example, in the case that the lightfrom the light emitting element 715 is emitted to the substrate 700, theshielding film may be provided between the first interlayer insulatingfilm 753 and the second interlayer insulating film 751. As in the casewith this, the shielding film has a opening portion so as to pass thelight from the light emitting element.

Furthermore, as was explained using FIG. 38, by providing an impurityregion overlapped with the gate electrode through an insulating film, itis possible to form an n-channel TFT resistive to the deteriorationresulting from hot-carrier effect. Consequently, a reliable lightemitting device can be realized.

Meanwhile, this embodiment shows only the configuration of the pixelportion and driver circuit. However, according to the manufacturingprocess in this embodiment, besides there, it is possible to form logiccircuits such as a signal division circuit, a D/A converter, anoperation amplifier, a γ-correction circuit on a same insulator.Furthermore, a memory or microprocessor can be formed.

The light emitting device manufactured, wherein a laser beam having aperiodic or uniform energy distribution is irradiated and a crystalgrain with a large grain size is formed. Thus, the light emitting deviceensures a good operational characteristic and high reliability. Thelight emitting device can be used as a display portion for an electronicappliance in various kinds.

Although the light from the light emitting element is emitted in thedirection of TFT, the light emitting element may face to the reversedirection. In this case, resin that is a mixed with a black die, carbon,or black pigments may be used for forming the bank. FIG. 48 shows across-sectional view of the light emitting device in which the lightfrom the light emitting element is emitted to the reverse direction tothe TFT.

FIG. 48 shows that the contact hole is formed to the gate insulatingfilm 952, the first interlayer insulating film 953, the secondinterlayer insulating film 951, and the third interlayer insulating film950. After the conductive film is formed on the third interlayerinsulating film 950, the wires 901 to 907 that are connectedelectrically to impurity regions of each TFT by etching the conductivefilm. These wires are formed by patterning an aluminum alloy film(aluminum film contains 1 wt % titanium) having 300 nm in thickness.There is not limited to the single layer structure, the double layerstructure may also be used. As materials for forming the wires, there isnot limited to Al and Ti. A portion of the wiring 906 doubles as thepixel electrode.

After forming the wires 901 to 907, the bank 912 is formed made from theresin material. The bank 912 is formed to expose a portion of the pixelelectrode 906 by patterning the resin having 1 to 2 μm in thicknessmixed with a black dye, carbon, or black pigments. As materials forresin, although polyimide, polyamide, acrylics, BCB (benzocyclobutene),and the like are mentioned typically, it is not limited to theabove-mentioned material.

The light emitting layer 913 is formed on the pixel electrode 906. Anopposed electrode (an anode of the light emitting element) made from thetransparent conductive film is formed to cover the light emitting layer913. As the transparent conductive film can be used a compound of indiumoxide and tin oxide, a compound of indium oxide and zinc oxide, zincoxide, tin oxide or indium oxide. A transparent conductive film addedwith gallium may also be used.

The light emitting element 915 is formed by the pixel electrode 906, thelight emitting layer 913, and the opposed electrode 914.

The shielding film 970 is effective in the external light reflected inwires 901 to 907 preventing going into an observer's eyes.

Incidentally, this embodiment can be implemented by combining any one ofEmbodiments 1 to 6.

Embodiment 9

This embodiment describes a pixel configuration of a light emittingdevice that is one of a semiconductor device of the present invention.FIG. 39 shows a cross-sectional view of a pixel of the light emittingdevice of this embodiment.

Reference numeral 911 denotes a substrate and reference numeral 912denotes an insulating film which becomes a base (hereafter referred toas a base film) in FIG. 39. A light transmitting substrate, typically aglass substrate, a quartz substrate, a glass ceramic substrate, or acrystalline glass substrate can be used as the substrate 911. However,the substrate used must be one able to withstand the highest processtemperature during the manufacturing processes.

Reference numeral 8201 denotes a switching TFT, reference numeral 8202denotes a current controlling TFT, and both are formed by n-channel TFTand p-channel TFTs respectively. When the direction of light emittedfrom the light emitting layer is toward bottom of the substrate (surfacewhere TFTs and the organic light emitting layer are not formed), theabove structure is preferable. However, the present invention is notlimited to this structure. The switching TFT and the current controllingTFT may be either n-channel TFTs or p-channel TFTs.

The switching TFT 8201 has an active layer containing a source region913, a drain region 914, LDD regions 915 a to 915 d, a separation region916, and an active layer including channel forming regions 917 a and 917b, a gate insulating film 918, gate electrodes 919 a and 919 b, a firstinterlayer insulating film 920, a source signal line 921 and a drainwiring 922. Note that the gate insulating film 918 and the firstinterlayer insulating film 920 may be common among all TFTs on thesubstrate, or may differ depending upon the circuit or the element.

Furthermore, the switching TFT 8201 shown in FIG. 39 is electricallyconnected to the gate electrodes 917 a and 917 b, becoming namely adouble gate structure. Not only the double gate structure, but also amulti gate structure (a structure containing an active layer having twoor more channel forming regions connected in series) such as a triplegate structure, may of course also be used.

The multi gate structure is extremely effective in reducing the offcurrent, and provided that the off current of the switching TFT issufficiently lowered, a capacitor connected to the gate electrode of thecurrent controlling TFT 8202 can be have its capacitance reduced to theminimum necessary. Namely, the surface area of the capacitor can be madesmaller, and therefore using the multi gate structure is effective inexpanding the effective light emitting surface area of the lightemitting elements.

In addition, the LDD regions 915 a to 915 d are formed so as not tooverlap the gate electrodes 919 a and 919 b through the gate insulatingfilm 918 in the switching TFT 8201. This type of structure is extremelyeffective in reducing the off current. Furthermore, the length (width)of the LDD regions 915 a to 915 d may be set from 0.5 to 3.5 μm,typically between 2.0 and 2.5 μm. Further, when using a multi gatestructure having two or more gate electrodes, the separation region 916(a region to which the same impurity element, at the same concentration,as that added to the source region or the drain region, is added) iseffective in reducing the off current.

Next, the current controlling TFT 8202 is formed having an active layercontaining a source region 926, a drain region 927, and a channelforming region 965; the gate insulating film 918; a gate electrode 930,the first interlayer insulating film 920; a source wiring 931; and adrain wiring 932. The current controlling TFT 8202 is a p-channel TFT inthis embodiment.

Further, the drain region 914 of the switching TFT 8201 is connected tothe gate electrode 930 of the current controlling TFT 8202. Although notshown in the figure, specifically the gate electrode 930 of the currentcontrolling TFT 8202 is electrically connected to the drain region 914of the switching TFT 8201 through the drain wiring (also referred to asa connection wiring) 922. The gate electrode 930 is a single gatestructure in this embodiment, however, the multi gate structure can bealso applied. The source wiring 931 of the current controlling TFT, 8202is connected to an power source supply line (not shown in the figure).

The structures of the TFTs formed within the pixel are explained above,but a driver circuit is also formed simultaneously at this point. A CMOScircuit, which becomes a basic unit for forming the driver circuit, isshown in FIG. 39.

A TFT having a structure in which hot carrier injection is reducedwithout an excessive drop in the operating speed is used as an n-channelTFT 8204 of the CMOS circuit in FIG. 39. Note that the term drivercircuit indicates a source signal line driver circuit and a gate signalline driver circuit here. It is also possible to form other logiccircuit (such as a level shifter, an A/D converter, and a signaldivision circuit).

An active layer of the n-channel TFT 8204 of the CMOS circuit contains asource region 935, a drain region 936, an LDD region 937, and a channelforming region 962. The LDD region 937 overlaps with a gate electrode939 through the gate insulating film 918.

Formation of the LDD region 937 on only the drain region 936 side is soas not to have drop the operating speed. Further, it is not necessary tobe very concerned about the off current with the n-channel TFT 8204, andit is good to place more importance on the operating speed. Thus, it isdesirable that the LDD region 937 is made to completely overlap the gateelectrode to decrease a resistance component to a minimum. It istherefore preferable to eliminate so-called offset.

Furthermore, there is almost no need to be concerned with degradation ofa p-channel TFT 8205 of the CMOS circuit, due to hot carrier injection,and therefore no LDD region need be formed in particular. Its activelayer therefore contains a source region 940, a drain region 941, and achannel forming region 961, and a gate insulating film 918 and a gateelectrode 943 are formed on the active layer. It is also possible, ofcourse, to take measures against hot carrier injection by forming an LDDregion similar to that of the n-channel TFT 8204.

The references numeral 961 to 965 are masks to form the channel formingregions 942, 938, 917 a, 917 b and 929.

Further, the n-channel TFT 8204 and the p-channel TFT 8205 have sourcewirings 944 and 945, respectively, on their source regions, through thefirst interlayer insulating film 920. In addition, the drain regions ofthe n-channel TFT 8204 and the p-channel TFT 8205 are mutually connectedelectrically by a drain wiring 946.

Next, there will be described a semiconductor fabricating device of thepresent invention that uses the forming of a semiconductor film, thecrystallization of an activation layer, the activation, or the stepusing laser annealing.

A manufacturing flow of the light emitting device of the presentinvention is shown in FIG. 40 as a flowchart. First, there is performedthe designing of a semiconductor device using CAD. Then, informationconcerning the shape of each designed mask for patterning asemiconductor film is inputted into a computer possessed by the laserapparatus.

On the other hand, the gate electrode is formed according to the markerformed on the substrate. The gate insulating film is formed to cover thegate electrode, and the amorphous semiconductor film is formed tocontact with the gate insulating film. After an amorphous semiconductorfilm is formed on a substrate, the substrate, on which the amorphoussemiconductor film has been formed, is set in the laser apparatus.

On the basis of inputted information concerning the masks, the computerdetermines each portion to be scanned with laser lights with referenceto the positions of the markers. Then, with reference to the formedmarkers, the laser lights are irradiated onto the portion to be scannedwith the laser lights, thereby partially crystallizing the semiconductorfilm.

Then, after the irradiation of the laser beams, a polycrystallinesemiconductor film obtained by the irradiation of the laser beams ispatterned and etched, thereby forming island-like semiconductor films.The timing of patterning of the polycrystalline semiconductor film ispossible to change appropriately according to the TFT design. Followingthis, there is performed a step for manufacturing a TFT from theseisland-like semiconductor films. The concrete step for manufacturing theTFT differs depending on the shape of the TFT. Representatively,however, a gate insulating film is formed and an impurity region isformed in the island-like semiconductor films. Then, an interlayerinsulating film is formed so as to cover the island-like semiconductorfilm, and a contact hole is established in the interlayer insulatingfilm. In this manner, there is obtained an exposed part of the impurityregion. Then, wiring is formed on the interlayer insulating film so asto contact the impurity region through the contact hole.

The semiconductor fabricating device may be used to conduct not onlysteps from forming of the amorphous semiconductor film to thecrystallization of the laser beam, but also steps from forming of thegate insulating film to the crystallization by the laser beam withoutexposing to the atmosphere in succession, or adding another steps insuccession.

The structure of this embodiment may be implemented by combining freelywith Embodiments 1 to 8.

Embodiment 10

In this embodiment, description is made on a construction of a pixel ofa light emitting device fabricated by the semiconductor fabricatingapparatus of the invention. FIG. 41 is a sectional view showing a pixelof the light emitting device according to the embodiment.

A reference numeral 1751 denotes an n-channel TFT whereas a numeral 1752denotes a p-channel TFT. The n-channel TFT 1751 includes a semiconductorfilm 1753, a first insulating film 1770, first electrodes 1754, 1755, asecond insulating film 1771, and second electrodes 1756, 1757. Thesemiconductor film 1753 includes a one-conductive type impurity regionof a first concentration 1758, a one-conductive type impurity region ofa second concentration 1759, and channel forming regions 1760, 1761.

The first electrodes 1754, 1755 and the channel forming regions 1760,1761 are in stacked relation with the first insulating film 1770interposed therebetween. The second electrodes 1756, 1757 and thechannel forming regions 1760, 1761 are in stacked relation with thesecond insulating film 1771 interposed therebetween.

The p-channel TFT 1752 includes a semiconductor film 1780, the firstinsulating film 1770, a first electrode 1782, the second insulating film1771, and a second electrode 1781. The semiconductor film 1780 includesa one-conductive type impurity region of a third concentration 1783, anda channel forming region 1784.

The first electrode 1782 and the channel forming region 1784 are instacked relation with the first insulating film 1770 interposedtherebetween. The second electrode 1781 and the channel forming region1784 are in stacked relation with the second insulating film 1771interposed therebetween.

The first electrode 1782 and the second electrode 1781 are electricallyinterconnected via a wiring 1790.

The semiconductor fabricating apparatus of the invention may be used inthe steps of forming, crystallizing and activating the semiconductorfilms 1785, 1780 and other processes using laser annealing.

According to the embodiment, the TFT (the n-channel TFT 1751 in thisembodiment), used as a switching device, applies a constant voltage tothe first electrode. The application of the constant voltage to thefirst electrode is effective to reduce the variations of threshold ascompared with an arrangement including a single electrode and to reduceOFF current.

In the TFT (the p-channel TFT 1752 in this embodiment) conducting agreater current than the TFT used as the switching device, the firstelectrode and the second electrode are electrically interconnected. Theapplication of the same voltage to the first and second electrodesprovides quick propagation of a depletion layer just as in asemiconductor film decreased in thickness, thus resulting in a decreasedsub-threshold voltage swing and an enhanced field effect mobility.Therefore, the TFT achieves a greater on current than a TFT including asingle electrode. Hence, the use of the TFT of this structure in a drivecircuit leads to a decreased drive voltage. Furthermore, the achievementof the increased on current permits the size reduction (channel width,in particular) of the TFT. This leads to an increased packaging density.

FIG. 42 is a flow chart showing the steps of fabricating a lightemitting device according to the invention. First, a semiconductordevice is designed by means of a CAD. Then, information indicative of aconfiguration of a patterning mask for the designed semiconductor filmis inputted to the computer of the laser irradiation equipment.

On the other hand, first electrodes are formed based on markers formedon the substrate. In this process, the first electrodes may be formed inparallel with the markers. Subsequently, a first insulating film isformed in a manner to cover the first electrodes. Then an amorphoussemiconductor film is formed in contacting relation with the firstinsulating film. After the formation of the amorphous semiconductor filmon the substrate, the substrate formed with the amorphous semiconductorfilm is loaded on the laser irradiation equipment.

According to the mask information inputted to the computer, the computerdefines an area to be scanned with the laser light with reference to theposition of the markers. With reference to the formed markers, the laserlight is irradiated on the area to be scanned for local crystallizationof the semiconductor film.

The laser irradiation is followed by sequential formation of a secondinsulating film and second electrodes. The polycrystalline semiconductorfilm formed by the laser irradiation is patterned and etched therebyforming semiconductor film islands. A timing at which thepolycrystalline semiconductor film is patterned may properly be changedaccording to the TFT design. In the subsequent steps, TFTs are formedfrom the semiconductor film islands. Although specific steps may varydepending upon the configurations of the TFTs, the steps typicallyinclude: forming impurity regions in the semiconductor film islands;forming an interlayer insulating film in a manner to cover the secondinsulating film and the second electrodes; forming contact holes in theinterlayer insulating film for partially exposing the impurity regions;and laying a wiring on the interlayer insulating film in a manner toestablish contact with the impurity regions via the contact holes.

Instead of being used only for the formation of the amorphoussemiconductor film and the irradiation of the laser light forcrystallization, the semiconductor fabricating apparatus of theinvention may be used in the process between the formation of the firstinsulating film and the formation of the second insulating film suchthat these steps may be sequentially performed without exposure to theatmosphere. Furthermore, the inventive apparatus may be operated forsequential performance of the above steps and other steps.

It is noted that this embodiment may be implemented in combination withany one of Embodiments 1 to 9.

Embodiment 11

This embodiment illustrates an example where the semiconductor device ofthe invention is used for forming a drive circuit (signal line drivecircuit or scanning line drive circuit) which is mounted on a pixelportion formed from an amorphous semiconductor film by way of TAB orCOG.

FIG. 43A illustrates an example where a drive circuit is mounted on TAB,which is used for interconnecting a pixel portion and a printed wiringboard formed with an external controller and the like. A pixel portion5001 is formed on a glass substrate 5000 and is connected with a drivecircuit 5002 via a TAB 5005, the drive circuit fabricated by thesemiconductor fabricating apparatus of the invention. The drive circuit5002 is also connected with a printed wiring board 5003 via the TAB5005. The printed wiring board 5003 is provided with a terminal 5004 forconnection with an external interface.

FIG. 43B illustrates an example where a drive circuit and a pixelportion are mounted by way of COG. A pixel portion 5101 is formed on aglass substrate 5100, on which a drive circuit 5102 fabricated by thesemiconductor fabricating apparatus of the invention is mounted. Thesubstrate 5100 is further provided with a terminal 5104 for connectionwith an external interface.

The TFT fabricated by the semiconductor fabricating apparatus of theinvention is further enhanced in the crystallinity of the channelforming region and hence, is capable of high speed operation. Thus, theTFT is more suitable for forming the drive circuit required of a fasteroperation than the pixel portion. In addition, a higher yield can beachieved by separately fabricating the pixel portion and the drivecircuit.

It is noted that this embodiment may be implemented in combination withany one of Embodiments 1 to 10.

Embodiment 12

In this embodiment, there will be described a relation between (i) thedistance between the centers of respective laser beams and (ii) anenergy density, in the case where the laser beams are made to overlapeach other. Note that in order to make it easier to understand theexplanation, a case where no slit is provided will be described.

In FIG. 45, the distribution of the energy density of each beam spot inthe center axis direction is shown using a solid line and thedistribution of the energy density of a beam spot obtained bysynthesizing the beam spots is shown using a broken line. In general,the value of the energy density of a beam spot in the center axisdirection is pursuant to the Gaussian distribution.

As to each beam spot before the synthesizing, it is assumed that thedistance in the center axis direction at which an energy density of 1/e²or higher of a peak value is satisfied is set as “1” and the distancebetween respective peaks is referred to as “X”. Also, as to the laserbeam after the synthesizing, peak values after the synthesizing and anincreased amount of the peak values from the average value of valleyvalues are referred to as “Y”. A relation between “X” and “Y” obtainedthrough a simulation is shown in FIG. 46. Note that in FIG. 46, “Y” isexpressed on a percentage basis.

It is possible to express an energy difference Y in FIG. 46 usingFormula 3 given below that is an approximate expression.Y=60−293X+340X ² (X is larger one of two solutions)  [Formula 3]

It can be seen from Formula 3 that in the case where it is desired toset the energy difference at around 5%, for instance, it is sufficientthat “X” is set almost equal to 0.584. It is ideal that “Y” becomesequal to zero. In this case, however, the lengths of beam spots areshortened, so that it is preferable that “X” is determined withconsideration given to the balance with throughput.

Next, there will be described a permissible range of “Y”. In FIG. 47,there is shown the distribution of the output (W) of a YVO₄ laser withrespect to its beam width in the center axis direction in the case whereits beam spot has an elliptic shape. The region specified by slopedlines is a range of the output energy that is necessary to obtainfavorable crystallinity and it can be seen that it is sufficient thatthe output energy of synthesized laser lights falls within a range offrom 3.5 to 6 W.

When the maximum value and the minimum value of the output energy of thebeam spot after the synthesizing barely fall within the output energyrange that is necessary to obtain the favorable crystallinity, theenergy difference Y, with which it is possible to obtain the favorablecrystallinity, is maximized. As a result, in the case shown in FIG. 47,the energy difference Y becomes ±26.3% and it can be seen that thefavorable crystallinity is obtained if the energy difference “Y” fallswithin the range described above.

It should be noted here that the range of the output energy that isnecessary to obtain the favorable crystallinity varies depending on therange of crystallinity that is judged as favorable. Also, thedistribution of the output energy varies depending on the shape of thebeam spot, so that the permissible range of the energy difference Y isnot necessarily limited to the value described above. A designer isrequired to determine the range of the output energy that is necessaryto obtain the favorable crystallinity as appropriate and to set thepermissible range of the energy difference Y from the distribution ofthe output energy of a laser used.

It is possible to implement this embodiment in combination with thefirst to eleventh embodiments.

Embodiment 13

Given as embodiments of electric equipment employing a semiconductordevice formed by the laser apparatus of the present invention is appliedare: a video camera; a digital camera; a goggle type display (headmounted display); a navigation system; an audio reproducing device (caraudio, an audio component, and the like); a laptop computer; a gamemachine; a portable information terminal (a mobile computer, a cellularphone, a portable game machine, an electronic book, etc.); and an imagereproducing device equipped with a recording medium (specifically, adevice equipped with a display device which can reproduce a recordingmedium such as a digital versatile disk (DVD), and can display theimage). Specific examples of the electric equipment are shown in FIGS.44A to 44H.

FIG. 44A shows a display device, which comprises a casing 2001, asupporting base 2002, a display portion 2003, speaker portions 2004, avideo input terminal 2005, etc. The light emitting device formed by thepresent invention is applied can be used for the display portion 2003.The semiconductor device is self-luminous and does not need a backlight,so that it can make a thinner display portion than liquid displaydevices can. The term display device includes every display device fordisplaying information such as one for a personal computer, one forreceiving TV broadcasting, and one for advertisement.

FIG. 44B shows a digital still camera, which comprises a main body 2101,a display portion 2102, an image receiving portion 2103, operation keys2104, an external connection port 2105, a shutter 2106, etc. The lightemitting device formed by the present invention is applied can be usedfor the display portion 2102, and other circuits.

FIG. 44C shows a laptop computer, which comprises a main body 2201, acasing 2202, a display portion 2203, a keyboard 2204, an externalconnection port 2205, a pointing mouse 2206, etc. The light emittingdevice formed by the present invention is applied can be used for thedisplay portion 2203, and other circuits.

FIG. 44D shows a mobile computer, which comprises a main body 2301, adisplay portion 2302, a switch 2303, operation keys 2304, an infraredray port 2305, etc. The light emitting device formed by the presentinvention is applied can be used for the display portion 2302, and othercircuits.

FIG. 44E shows a portable image reproducing device equipped with arecording medium (a DVD player, to be specific). The device comprises amain body 2401, a casing 2402, a display portion A 2403, a displayportion B 2404, a recording medium (DVD or the like) reading portion2405, operation keys 2406, speaker portions 2407, etc. The displayportion A 2403 mainly displays image information whereas the displayportion B 2404 mainly displays text information. The light emittingdevice formed by the present invention is applied can be used for thedisplay portions A 2403 and B 2404, and other circuits. The term imagereproducing device equipped with a recording medium includes domesticgame machines.

FIG. 44F shows a goggle type display (head mounted display), whichcomprises a main body 2501, display portions 2502, and arm portions2503. The light emitting device formed by the present invention isapplied can be used for the display portions 2502, and other circuits.

FIG. 44G shows a video camera, which comprises a main body 2601, adisplay portion 2602, a casing 2603, an external connection port 2604, aremote control receiving portion 2605, an image receiving portion 2606,a battery 2607, an audio input portion 2608, operation keys 2609,eyepiece portion 2610 etc. The light emitting device formed by thepresent invention is applied can be used for the display portion 2602,and other circuits.

FIG. 44H shows a portable telephone, which comprises a main body 2701, acasing 2702, a display portion 2703, an audio input portion 2704, anaudio output portion 2705, operation keys 2706, an external connectionport 2707, an antenna 2708, etc. The light emitting device formed by thepresent invention is applied can be used for the display portion 2703,and other circuits. If the display portion 2703 displays whitecharacters on a black background, power consumption of the cellularphone can be reduced.

The light emitting device can be used also in a front or rear projectorbesides above-mentioned electronic apparatuses.

As described above, the application range of the light emitting deviceto which the present invention is applied is very wide and electricequipment of every field can employ the device. The electric equipmentsin this embodiment may use any configuration of semiconductor devicesshown in Embodiments 1 to 12.

Embodiment 14

The construction of a pixel of a light-emitting apparatus of the presentinvention will be described with reference to FIG. 49.

In FIG. 49, a base film 6001 is formed on a substrate 6000 and atransistor 6002 is formed on this base film 6001. The transistor 6002includes an active layer 6003, a gate electrode 6005, and a gateinsulating film 6004 sandwiched between the active layer 6003 and thegate electrode 6005.

It is preferable that a polycrystalline semiconductor film is used asthe active layer 6003 and it is possible to form this polycrystallinesemiconductor film using the laser irradiation apparatus of the presentinvention.

It should be noted here that the active layer may be formed usingsilicon germanium, in addition to silicon. In the case where the silicongermanium is used, it is preferable that the concentration of germaniumis set at around 0.01 to 4.5 atomic %. Also, there may be used siliconto which carbon nitride has been added.

Also, it is possible to use a silicon oxide film, a silicon nitridefilm, or a silicon oxynitride film as the gate insulating film 6004.Also, it is possible to use a film obtained by laminating these films (afilm obtained by laminating an SiN film on an SiO₂ film, for instance)as the gate insulating film. Also, when the SiO₂ film is used, TEOS(Tetraethyl Orthosilicate) is mixed with O₂ using a plasma CVD methodand discharging is performed at an reaction pressure of 40 Pa, asubstrate temperature of 300 to 400° C., a high frequency (13.56 MHz),and an electric power density of 0.5 to 0.8 W/cm², thereby forming asilicon oxide film. The silicon oxide film produced in this manner isconverted into the gate insulating film through thermal annealing at 400to 500° C. performed afterward. In this manner, it is possible to obtainfavorable characteristics. Also, it is possible to use an aluminumnitride film as the gate insulating film. Aluminum nitride hasrelatively high heat conductivity and makes it possible to effectivelydiffuse heat generated by a TFT. Also, after a silicon oxide film, asilicon oxynitride film, or the like that does not contain aluminum isformed, an aluminum nitride film may be laminated on this film and aresultant film may be used as the gate insulating film. Also, an SiO₂film formed with an RF sputtering method, whose target is Si, may beused as the gate insulating film.

Also, the gate electrode 6005 is formed using an element selected fromthe group consisting of Ta, W, Ti, Mo, Al, and Cu. Alternatively, thegate electrode 6005 is formed using an alloy material or a compoundmaterial whose main ingredient is the element described above. Also,there may be used a semiconductor film typified by a polycrystallinesilicon film doped with an impurity element such as phosphorus. Also, inplace of a single-layer conductive film, there may be used a conductivefilm obtained by laminating a plurality of layers.

For instance, it is preferable that a multi-layer conductive film isformed using a combination where a first conductive film is formed usingtantalum nitride (TaN) and a second conductive film is formed using W, acombination where the first conductive film is formed using tantalumnitride (TaN) and the second conductive film is formed using Ti, acombination where the first conductive film is formed using tantalumnitride (TaN) and the second conductive film is formed using Al, or acombination where the first conductive film is formed using tantalumnitride (TaN) and the second conductive film is formed using Cu. Also, asemiconductor film typified by a polycrystalline silicon film doped withan impurity element, such as phosphorous, or an AgPdCu alloy may be usedas the first conductive film and the second conductive film.

Also, the present invention is not limited to the two-layer constructionand there may be used a three-layer construction where a tungsten film,an alloy (Al—Si) film of aluminum and silicon, and a titanium nitridefilm are laminated in succession, for instance. Also, in the case wherethe three-layer construction is used, a tungsten nitride film may beused in place of the tungsten film, an alloy film (Al—Ti) of aluminumand titanium may be used in place of the alloy (Al—Si) film of aluminumand silicon, and a titanium film may be used in place of the titaniumnitride film.

It should be noted here that it is important that an optimum etchingmethod and an optimum kind of etchant are selected as appropriateaccording to the materials of the conductive films.

Also, the transistor 6002 is covered with a first interlayer insulatingfilm 6006, and a second interlayer insulating film 6007 and a thirdinterlayer insulating film 6008 are laminated on the first interlayerinsulating film 6006.

As the first interlayer insulating film 6006, it is possible to use asingle-layer film that is a silicon oxide film, a silicon nitride film,or a silicon oxynitride film produced using a plasma CVD method or asputtering method. Alternatively, it is possible to use a multi-layerfilm obtained by laminating them. Also, as the first interlayerinsulating film 6006, there may be used a film obtained by laminating asilicon oxynitride film, in which the mole fraction of nitrogen ishigher than that of oxygen, on a silicon oxynitride film in which themole fraction of oxygen is higher than that of nitrogen.

It should be noted here that when a heating treatment (heat treatment at300 to 550° C. for 1 to 12 hours) is performed after the formation ofthe first interlayer insulating film 6006, it becomes possible toterminate (hydrogenate) the dangling bonds of a semiconductor containedin the active layer 6003 with hydrogen contained in the first interlayerinsulating film 6006.

Also, it is possible to use a non-photosensitive acrylic film as thesecond interlayer insulating film 6007.

As the third interlayer insulating film 6008, there is used a film thatis resistant to permeating of a material (such as moisture or oxygen)which will accelerate the degradation of a light-emitting element, incomparison with other insulating films. Representatively, it ispreferable that there is used a DLC film, a carbon nitride film, or asilicon nitride film formed using an RF sputtering method, for instance.

Also, in FIG. 49, reference numeral 6010 denotes an anode, numeral 6011an electroluminescence layer, and numeral 6012 a cathode, with a portionin which the anode 6010, the electroluminescence layer 6011, and thecathode 6012 overlap each other corresponding to a light-emittingelement 6013. The transistor 6002 is a driving transistor that controlsa current supplied to the light-emitting element 6013 and is connectedto the light-emitting element 6013 in series directly or via anothercircuit element.

The electroluminescence layer 6011 has a construction where alight-emitting layer is solely used or a construction where a pluralityof layers including a light-emitting layer are laminated.

The anode 6010 is formed on the third interlayer insulating film 6008.Also, an organic resin film 6014 used as a partition wall is formed onthe third interlayer insulating film 6008. The organic resin film 6014has an opening portion 6015, and the anode 6010, the electroluminescencelayer 6011, and the cathode 6012 are made to overlap each other in theopening portion, thereby forming the light-emitting element 6013.

In addition, a protective film 6016 is formed on the organic resin film6014 and the cathode 6012. As this protective film 6016, like in thecase of the third interlayer insulating film 6008, there is used a filmthat is resistant to the permeating of a material (such as moisture oroxygen) which will accelerate the degradation of the light-emittingelement, in comparison with other insulating films. Representatively, itis preferable that there is used a DLC film, a carbon nitride film, or asilicon nitride film formed with an RF sputtering method, for instance.Also, as the protective film, there may be used a film obtained bylaminating the aforementioned film that is resistant to the permeatingof a material, such as moisture or oxygen, on a film that is lessresistant to the permeating of the material such as moisture or oxygenin comparison with the resistant film.

Also, before the formation of the electroluminescence layer 6011, theorganic resin film 6014 is heated under a vacuum atmosphere in order toremove adsorbed moisture, oxygen, or the like. In more detail, a heatingtreatment is performed under a vacuum atmosphere at 100 to 200° C. foraround 0.5 to 1 hour. Preferably, the pressure is set at 3×10⁻⁷ Torr orbelow and, if possible, it is the most preferable that the pressure isset at 3×10⁻⁸ Torr or below. In addition, in the case where theelectroluminescence layer is formed after the heating treatment isperformed on the organic resin film under the vacuum atmosphere, itbecomes possible to further enhance reliability by maintaining theorganic resin film under the vacuum atmosphere until immediately beforethe formation of the electroluminescence layer.

Also, it is preferable that the end portions of the opening portion 6015of the organic resin film 6014 are rounded off in order to prevent asituation where a hole is opened in the electroluminescence layer 6011,which has been formed so as to partially overlap the organic resin film6014, at these end portions. In more detail, it is preferable that theradius of curvature of a curve drawn by the cross section of the organicresin film at the opening portion is around 0.2 to 2 μm.

With the construction described above, it becomes possible to obtainfavorable coverage concerning the electroluminescence layer and thecathode formed in later steps and to prevent a situation where a shortcircuit between the anode 6010 and the cathode 6012 occurs in a holeformed in the electroluminescence layer 6011. Also, by alleviating thestress of the electroluminescence layer 6011, it becomes possible toreduce a defect called “shrinkage” whereby the area of a light-emittingregion is reduced, and to enhance reliability.

It should be noted here that FIG. 49 shows an example where an acrylicresin film having positive type photosensitivity is used as the organicresin film 6014. There are two types of photosensitive organic resin: apositive type where each portion exposed with an energy line of light,an electron, or an ion will be removed; and a negative type where eachexposed portion will be left. In the present invention, there may beused an organic resin film of the negative type. Also, the organic resinfilm 6014 may be formed using photosensitive polyimide.

In the case where the organic resin film 6014 is formed using acrylic ofthe negative type, the end portions of the opening portion 6015 have across section with an S shape. It is preferable that the radius ofcurvature of a curve between the upper end portion and the lower endportion of the opening portion is set at 0.2 to 2 μm in this case.

It is possible to use a transparent conductive film as the anode 6010.In addition to ITO, there may be used a transparent conductive filmproduced by mixing 2 to 20% of zinc oxide (ZnO) to indium oxide. In FIG.49, ITO is used as the anode 6010. This anode 6010 may be polished witha CMP method and be subjected to wiping/cleaning that uses apolyvinyl-alcohol-based porous body (Bellclean cleaning), therebyflattening the surface of the anode 6010. Also, after the polishing withthe CMP method, the surface of the anode 6010 may be subjected to theirradiation of ultraviolet rays, oxygen plasma processing, or the like.

Also, it is possible to form the cathode 6012 using a publicly knownanother material so long as it is possible to obtain a conductive filmwith a small work function. For instance, it is preferable that there isused Ca, Al, CaF, MgAg, AlLi, or the like.

It should be noted here that FIG. 49 shows a construction where lightemitted from the light-emitting element is irradiated on the substrate6000 side, although the light-emitting device may have a constructionwhere the light is directed toward a side opposite to the substrate.

Also, the transistor 6002 and the anode 6010 of the light-emittingelement are connected to each other in FIG. 49, although the presentinvention is not limited to this construction. For instance, thetransistor 6002 and the cathode 6001 of the light-emitting element maybe connected to each other. In this case, the cathode is formed on thethird interlayer insulating film 6008 using TiN or the like.

It should be noted here that it is preferable that in actual cases,after there is obtained a semiconductor device under the state shown inFIG. 49, this semiconductor device is further packaged (sealed) using aprotective film (laminated film, ultraviolet curing resin film, or thelike) that is high in air tightness and achieves less degassing or usinga translucent cover material, thereby preventing the exposure to theoutside air. When doing so, if the inside of the cover material isplaced under an inert atmosphere or a hygroscopic material (bariumoxide, for instance) is provided inside thereof, the reliability of anOLED is improved.

It should be noted here that the present invention is not limited to theproduction method described above and it is possible to perform theproduction with a publicly known method. Also, it is possible to freelycombine this embodiment with the Embodiments 1 to 13.

In the present invention, laser lights are not scanned and irradiatedonto the entire surface of a semiconductor film but are scanned so thatat least each indispensable portion is crystallized to a minimum. Withthe construction described above, it becomes possible to save a timetaken to irradiate the laser lights onto each portion to be removedthrough patterning after the crystallization of the semiconductor film,which makes it possible to significantly shorten a time taken to processone substrate.

Also, by having a plurality of laser lights overlap each other andhaving the laser lights complement each other in each portion having alow energy density, it becomes possible to enhance the crystallinity ofa semiconductor film with efficiency in comparison with a case where theplurality of laser lights are not made to overlap each other and areused independently of each other.

It should be noted here that in the embodiments described above, therehas been described a case where laser lights oscillated from a pluralityof laser oscillation apparatuses are synthesized and used, although thepresent invention is not necessarily limited to this construction. It ispossible to solely use one laser oscillation apparatus if the outputenergy of the laser oscillation apparatus is relatively high and it ispossible to obtain an energy density having a desired value withoutreducing the area of its beam spot. Note that even in this case, byusing the slit, it becomes possible to shield each portion of the laserlight where the energy density is low, and to control the width of thebeam spot in accordance with pattern information.

What is claimed is:
 1. A manufacturing method for a semiconductor devicecomprising: forming a semiconductor film over a substrate; outputting aplurality of laser lights from a plurality of laser oscillationapparatuses; forming a first beam spot by partially overlapping beamspots of the plurality of laser lights; controlling a width of a slit bya computer; cutting a low energy density of the first beam spot by theslit; scanning the semiconductor film with the first beam spot in afirst direction; scanning the semiconductor film with a second beam spotin a second direction after the scanning in the first direction, andwherein the first direction is set perpendicular to the seconddirection, wherein the first direction is set parallel to a direction inwhich carriers move in channel formation regions in a thin filmtransistors, and wherein the first beam spot is scanned after cuttingthe low energy density of the first beam spot to a region of thesemiconductor film determined by a pattern information.
 2. Amanufacturing method for a semiconductor device according to claim 1,wherein the first beam spots of the plurality of laser lights arepartially overlapped so that centers of the first beam spots draws astraight line on the semiconductor film.
 3. A manufacturing method for asemiconductor device according to claim 1, wherein cutting the lowenergy density of first beam spot by the slit is performed after theoverlapping.
 4. A manufacturing method for a semiconductor deviceaccording to claim 1, wherein the laser oscillation apparatuses use atleast one kind of laser selected from the group consisting of a YAGlaser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, a glass laser, a rubylaser, an alexandrite laser, a Ti: sapphire laser, and a Y₂O₃ laser. 5.A manufacturing method for a semiconductor device according to claim 1,further comprising synchronizing the slit and the plurality of laseroscillation apparatuses.
 6. A manufacturing method for a semiconductordevice according to claim 1, wherein the laser lights arecontinuous-oscillation laser lights.
 7. A manufacturing method for asemiconductor device according to claim 1, wherein the laser lights arethe second harmonic.
 8. A manufacturing method for a semiconductordevice according to claim 1, wherein the scanning direction and thecenter axis of the first beam spot are set vertical to each other.
 9. Amanufacturing method for a semiconductor device comprising: forming asemiconductor film over a substrate; outputting a plurality of laserlights from a plurality of laser oscillation apparatuses; forming afirst beam spot by partially overlapping beam spots of the plurality oflaser lights; controlling a width of a slit by a computer; cutting a lowenergy density of the first beam spot by the slit; scanning thesemiconductor film with the first beam spot in a first direction;scanning the semiconductor film with a second beam spot in a seconddirection after the scanning in the first direction, and enhancingcrystallinity in a region determined by a pattern information byscanning the first beam spot on the region of the semiconductor filmdetermined by the pattern information, and wherein the first directionis set perpendicular to the second direction, wherein the firstdirection is set parallel to a direction in which carriers move inchannel formation regions in a thin film transistors, and wherein thefirst beam spot is scanned after cutting the low energy density of thebeam spot to a region of the semiconductor film determined by thepattern information.
 10. A manufacturing method for a semiconductordevice according to claim 9, wherein the first beam spots of theplurality of laser lights are partially overlapped so that centers ofthe first beam spots draws a straight line on the semiconductor film.11. A manufacturing method for a semiconductor device according to claim9, wherein cutting the low energy density of first beam spot by the slitis performed after the overlapping.
 12. A manufacturing method for asemiconductor device according to claim 9, wherein the laser oscillationapparatuses use at least one kind of laser selected from the groupconsisting of a YAG laser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, aglass laser, a ruby laser, an alexandrite laser, a Ti: sapphire laser,and a Y₂O₃ laser.
 13. A manufacturing method for a semiconductor deviceaccording to claim 9, further comprising synchronizing the slit and theplurality of laser oscillation apparatuses.
 14. A manufacturing methodfor a semiconductor device according to claim 9, wherein the laserlights are continuous-oscillation laser lights.
 15. A manufacturingmethod for a semiconductor device according to claim 9, wherein thelaser lights are the second harmonic.
 16. A manufacturing method for asemiconductor device according to claim 9, wherein the scanningdirection and the center axis of the first beam spot are set vertical toeach other.
 17. A manufacturing method for a semiconductor devicecomprising: forming a semiconductor film over a substrate; outputting aplurality of laser lights from a plurality of laser oscillationapparatuses; forming a first beam spot by partially overlapping beamspots of the plurality of laser lights; controlling a width of a slit bya computer; cutting a low energy density of the first beam spot by theslit; scanning the semiconductor film with the first beam spot in afirst direction; scanning the semiconductor film with a second beam spotin a second direction after the scanning in the first direction, andenhancing crystallinity in a region determined by a pattern informationby scanning the first beam spot on the region of the semiconductor filmdetermined by the pattern information; and forming an island-likesemiconductor film having crystallinity by patterning the region, inwhich the crystallinity has been enhanced, using the patterninformation, and wherein the first direction is set perpendicular to thesecond direction, wherein the first direction is set parallel to adirection in which carriers move in channel formation regions in a thinfilm transistors, and wherein the beam spot is scanned after cutting thelow energy density of the first beam spot to a region of thesemiconductor film determined by the pattern information.
 18. Amanufacturing method for a semiconductor device according to claim 17,wherein the first beam spots of the plurality of laser lights arepartially overlapped so that centers of the first beam spots draws astraight line on the semiconductor film.
 19. A manufacturing method fora semiconductor device according to claim 17, wherein cutting the lowenergy density of first beam spot by the slit is performed after theoverlapping.
 20. A manufacturing method for a semiconductor deviceaccording to claim 17, wherein the laser oscillation apparatuses use atleast one kind of laser selected from the group consisting of a YAGlaser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, a glass laser, a rubylaser, an alexandrite laser, a Ti: sapphire laser, and a Y₂O₃ laser. 21.A manufacturing method for a semiconductor device according to claim 17,further comprising synchronizing the slit and the plurality of laseroscillation apparatuses.
 22. A manufacturing method for a semiconductordevice according to claim 17, wherein the laser lights arecontinuous-oscillation laser lights.
 23. A manufacturing method for asemiconductor device according to claim 17, wherein the laser lights arethe second harmonic.
 24. A manufacturing method for a semiconductordevice according to claim 17, wherein the scanning direction and thecenter axis of the first beam spot are set vertical to each other.
 25. Amanufacturing method for a semiconductor device according to claim 1,wherein the semiconductor film is amorphous silicon film.
 26. Amanufacturing method for a semiconductor device according to claim 9,wherein the semiconductor film is amorphous silicon film.
 27. Amanufacturing method for a semiconductor device according to claim 17,wherein the semiconductor film is amorphous silicon film.